(Music)
Thank you very much, good evening, welcome, thanks for coming, and I'll talk to you a little bit tonight
about mammoths on the Channel Islands and as
Bryson mentioned there have been some recent finds on Santa Rosa Island
and some of the people who did the excavating are actually standing at the
back of the room there and they are they can raise their
hands there and identify themselves that's Monica Bugbee and Justin Wilkins
from the Mammoth Hot Springs site in South Dakota and if you're ever cruising
around in the northern Great Plains and you happen to pass through Hot Springs,
South Dakota on your way to Black Hills or Mount Rushmore or Sturgis for a
motorcycle rally be sure to stop in at Hot Springs and and go visit the museum
there where they've actually constructed a museum over a mammoth dig
site so how's that for a dedication to the study of mammoths so anyway we're
we're happy to have some of the esteemed mammoth paleontologists in the audience
tonight and without further ado I'll let them go ahead and give the talk that I
was going to give. (laughter) just kidding, anyway. I'm happy to be here it's always great
to talk about the Channel Islands to an audience that is a local audience
here that knows the Channel Islands and loves them and appreciates them and
that's that's a wonderful thing. other places where I talk about it they ask me
where the Channel Islands are except in places like the UK where they say
they're not in California they're off the coast of Britain so that's different
Channel Islands. first of all can everyone hear me all right? okay and back
in the control room there is there any possibility of extinguishing this light
or dimming it at least or something or maybe I can go get my sunglasses whoa
it's very bright yeah ah there we go I'm back okay is that okay all right so
Mammoths on the Channel Islands: How and Did They Get There. we'll talk a little
bit about both of those things and will even talk a little bit about why they're
not there now and that is very controversial and we'll just jump right
into the controversy when we get to that point. one thing too that I wanted to be
sure to say here is that our studies on the Channel Islands of mammoths and
indeed all of the geologic studies that we've done on the Channel Islands have
been a group effort I'm with the US Geological Survey USGS but we also work
closely of course with the National Park Service where these islands that we've
been finding the mammoths are located and also the Nature Conservancy for parts
of Santa Cruz Island. The Natural History Museum of Los Angeles County has been
very helpful to us in a lot of our paleontological studies with our smaller
fossils- marine invertebrates and things like that- and then I mentioned the
mammoth site in South Dakota and they have the coolest logo of all and they
are represented by people who I introduced you to already and they have
had in their past for a long time people involved in research here on the Channel
Islands, particularly the late Dr. Larry Akenbroad, who some of you might know
he made trickling visits to California, he's a retired Northern Arizona
University professor who then set up and dedicated his retirement years to the
mammoth site in South Dakota and we miss him a lot but we were trying to carry on
his legacy with continued studies of mammoths. so mammoths in North America
during the last major glacial period the last of the most recent of the ice ages
which was about 25,000 to about 12,000 years ago we had two common
species of mammoths in North America one of them the whoops whoa
let's go back there we go and the laser pointer is right up above here you got
to pick it very carefully here because it's up above the left right buttons. at
any rate the Columbian mammoth or Mammuthus colombi is indicated by these
red dots where the the sites are where it's been found some of them ranged up
pretty far north but not very many and most of our sites are down here in the
western and southwestern United States and a big concentration here in Florida
as well. but the woolly mammoth which a lot of people associate with the ice
ages is more of a northern species we have a lot of sites here in Alaska and
northwestern Canada and then a lot of sites in the northern United States, not
so many sites in Canada which you might expect to see except for the fact that
that's where the ice sheets were so or a major part of the last glacial period
that was all covered by a big thick ice sheet so a lot of that part of the world
what pretty much looked the way Greenland does today so that's why we don't have a
lot of mammoth sites there but we have lots of mammoth sites around it in the
northern part. so those are our two most common species of mammoths in North
America but here in California and adjacent to the Channel Islands we had a
third species: Mammuthus exilis, or the pygmy mammoth which, exilis meaning
'exiled' meaning exiled to these islands but not through some punishment/
banishment or something like that they did this voluntarily and I'll show you
how in a little bit here. and one thing to note here is the present distance
from the closest mainland locality which would be slung right around here near
Oxnard over to the closest Channel Island which would be east Anacapa is
presently at about 20 kilometers okay. multiply that by 1.6 and that's how many
miles you talking about 30-some miles something on that order other way around
thank you I was testing you just to see how awake you were, very good.
anyway as you can see 20 kilometers as I was saying and keep that figure in mind
because we'll see how that changes when we go into the past. thank you 14 miles.
so at any rate mammoth remains have been found at a number of locations on three
of the northern Channel Islands: a few of them on Santa Cruz but only in the
western part and none of these have been found in place as far as I know I could
be wrong about that but I think that's correct; lots of sites on Santa Rosa
Island and we'll see examples of those; and we have a few sites on San Miguel
Island as well and I'll show you some of those too. in fact let's start with San
Miguel Island here's some that are some of the first that I ever saw this is a
photograph I took in 1976 and these two people Diana Johnson and Don Johnson
were two people that did a lot of work here in the 1960s on the Channel Islands
and how many people have seen the caliche forest on San Miguel Island, or
have heard of it? that was actually identified and named by Don Johnson okay
and that's his wife Diana and they did this work early in the mid-60s before
many people were working on the Channel Islands and Don managed to find a piece
of Cyprus charcoal near this mammoth tusks and that's been radiocarbon dated
at around 18,800 years. that puts us right smack
in the middle of the last glacial period remember I said that was about 25,000 years to
about 12,000 years or so ago well that's really right in the middle of the last
glacial period and as you'll see when we get further on a lot of our mammoth ages
has kind of fallen to that time span, not all of them. here's some that we're also
done not too far away from where those last two sites are near Running Springs
in western San Miguel Island but these were done just a couple of years ago by
by a couple of us with the US Geological Survey. this is one of my cohorts Jeff
Bugatti and he is pointing to some snails that are right
near this tusk which is hanging out here and then in this gully up above there's
other fragments, other mammoth remains and more snails. and Jeff has been kind of a
pioneer in trying to resurrect the capability of using snails for
radiocarbon dating. a long time we thought that they weren't very good, it
turns out some are not so good but a lot of land snails and those that live on
San Miguel Island and Santa Rosa Island are actually pretty good for radiocarbon
dating and see these are the numbers we're getting from here around 19,000
again pretty close to what we saw in that last picture but here we've got
some younger ones so these mammoth remains apparently are a bit younger
than these which are lower in a stratigraphic sense from these others so
you can see we're spanning a lot more of the last glacial period here just at
this one particular site. some of them are undated but we keep finding them. one
of the rangers this is Luis Cuevas who's the head ranger on Santa Rosa Island,
she actually grew up on Santa Rosa Island as a matter of fact, and she's pointing to
this feature right here and a big pile of river gravel that's exposed in
Bechers Bay and if we do a close-up: look at that it's a mammoth tusk. pretty
beat up and weathering away rapidly and I don't even know if it's still exposed
there or not, does anyone know? No. Brandi is telling me it's gone now ok. but this
kind of thing pops up every now and then and we we find them periodically.
this is now retired Bill Faulkner from the Park Service here serving as scale
for the first complete pygmy mammoth skeleton about 12,800
years old and one of the excavators for this was Don Morris who is
retired archaeologist for Channel Islands National Park who is also in
the audience here tonight and keep me honest on mammoth history here along
with the two Hot Springs people. I got a lot of people checking on me here
tonight so I'm not going to make any more
mistakes about metric conversions I can assure you of that. at any rate you can
see this a reproduction of this cast of this over in the Channel Islands Visitor
Center, just right across the the courtyard here on days when that's open
and I believe it's now in the Santa Barbara County Museum, is that correct? the
actual specimen itself? and phenomenal find. this is one of the few times where
we've really been lucky here in California to be able to have someone
discover this kind of a nearly complete skeleton and it will give you an idea of
just sort of what the size of these pygmy mammoths are they are significantly
smaller you will see another picture that will illustrate that very
graphically. and here's our two superstars from Mammoth Hot Springs,
South Dakota, from the hot spring site in South Dakota. Monica and Justin who you
just saw a minute ago here they are when they're really doing their work they're
not standing upright and clean and showered and well dressed and everything
this is what they usually look like and here they are excavating this nearly
complete skull and it has a pair of tusks attached to it there's one of them
sticking out right there this was done just literally in the last couple of
weeks and if you are a subscriber to the Ventura County Star you probably read
the stories about the discovery and then there was a follow-up story about how it
was airlifted out and it's a spectacular find. and these two young superstars are
going to be studying this and learning more about it and we hope to find a lot
more information about it. what we do know from a couple of preliminary
radiocarbon ages it is likely younger than about 13,250
years so like the previous photo that I showed you it's on the
young side we're still in the last glacial period but we're really near the
tail end of that okay and we're actually getting close to the time when we start
to see the arrival of humans on the Channel Islands in those early days as
well and we'll return to that topic too. So mammoth ancestry and this is specifically
mammoth ancestry for North America now that we're talking about I mentioned the
Columbian mammoth- here it is right here- but it had an ancestor called Mammuthus
meridionalis and this was probably an immigrant from Asia we don't know but
we're pretty sure that's the case but it's been around a long time we have
dates on this particular species of mammoths from Anza Borrego Desert State
Park in San Diego County. anybody been there? a lot of people, good. and there
they go back to about 1.8 million years okay so that takes us way back into the
Ice Ages to earlier part of that Ice Age period that we call the Pleistocene and
that was apparently the ancestor of the Colombian mammoth (Mammuthus columbi)
which we think probably evolved here in North America and that in turn was the
ancestor we're pretty sure of Mammuthus exilis or the pygmy mammoth which
evolved on the Channel Islands. And just to give you some size
comparison here's a scale in meters so in feet that would be.... I'm not even going
to try it. not even going to try it. anyway you can see these were little
guys. these were little. there you go thank you. so you can see they were
pretty little okay so these are the kinds of guys that you you know wouldn't
mind you know pet sitting for a while and in your backyard they were probably
just as cute in their day as the Channel Islands fox is cute in its current day
and so we would have loved to have seen them but we'll do our best to use our
imaginations instead. so there on the Channel Islands, Colombian mammoths
somehow got out to the Channel Islands and then through time evolved down to
the smaller size. why did they evolve down to a smaller size? well part of the
reason is that one thing there's no particular advantage to being large if
you're out on an island where there aren't any predators that you have to worry
about you can be smaller and not have to appear
fearsome to a potential predator. But probably more importantly there's every
good reason to get smaller because little guys can find enough to eat and
you've got limited areas to like an island for the food resources and things
like that. The big guys might go hungry because there's maybe not quite as much
to munch on out there. So through time they tend to be selected down towards
the smaller forms: smaller and smaller forms. We don't know how long that takes.
if we know that it happens commonly when animals migrate to islands and get
isolated there's a general rule in biogeography that if they are size of a
pig or larger they tend to get smaller. Another good example from here in the
United States are the key deer in Florida which you can see if you go to
Big Pine Key just cruise around some of the back roads some eventually you'll
run into them like cohort Randy from the USGS who's here in the front row and I have
seen these guys on Big Pine Key and they are much much smaller than the sort of
deer that we're used to in Colorado where we live. But at any rate this is
probably how the dwarfing process took place is from limited resources on an
island every good reason to get smaller and no good reason to stay large but
then the question becomes why how did they get out there in the first place?
and we know that this was something that was an island process because we find
both Colombian mammoths but pygmy mammoths as well on the Channel Islands,
but no pygmy mammoths on the mainland. okay so that tells us that the
Colombians came out, dwarfed down to the pygmy sizes, and stayed there and were
isolated but we didn't have a- whether we had a reverse process or not we don't
know but at least it wasn't enough for pygmy mammoths to somehow get back on
the mainland because we've never found any. okay so looks like an island process.
but the question is how do they get there. so for years and years virtually
all researchers appealed to former land bridges and this is kind of like looking
at exploratory maps from the early European
era and exploration when people thought that Baja California was an island and
all kinds of crazy things and there's a lot of imagination in these things and
what you're seeing here are some of the kinds of land bridges that were
constructed by various researchers who study these but there's always a bridge
okay always a bridge coming across here somewhere or another bridge like this
you know some of them really quite elaborate as you can see here a lot more
electoral districts in the state of California in those days but at any rate
some of these are ideas that go back into the 30s and 40s and 50s but all the
way up to the 70s as well. however what's interesting is that there is no
geological or geophysical evidence at all, whatsoever, that such land bridges
ever existed, none, not a shred. okay and in addition the fact that we find only
pygmy mammoths and not other mammals. If there were other land- if there were
truly land bridges- and there were mammoths going across to the islands on
them, why didn't the saber-toothed cats come along as well? do you think they
would just say no way man that's going to be an island someday, I'm not going
near that. Cats can swim yeah but we don't like it you know they go right
after it, of course they would and we'd see a lot of the other Ice Age mammals
wandering across as well. why only mammoths then on the islands? okay? Nobody
could answer this question and what's interesting is that the evidence for
these land bridges- the only piece of evidence- was just the presence of the
pygmy mammoths. So people actually used that as the explanation
that there had to be a land bridge; all the geologic and geophysical evidence to
the contrary, forget about it, we're not going to worry about that, it had to be a
land bridge because the pygmy mammoths were there. Okay. Well as it turns out no
evidence for that and there still isn't and that's because it didn't happen. Now
recall that we have this distance which I will give in metric terms: 20
kilometers from Oxnard over to Anacapa but to get to a real Island you're
looking more at around 30 kilometers or so to get to Eastern Santa Cruz. Recall
too we haven't found any mammoths on Anacapa but on the other hand they're
very tiny islands very easily could have been eroded away. but the shallowest zone
here, okay, the absolute shallowest zone is around 230 to 240 meters depth, okay.
let's keep that number in mind, okay, that's a that's pretty deep water even
you know for a thing like the Pacific coast where we we drop off fairly
quickly, but that is as shallow as it gets, okay. however things were different
during ice ages okay. here's the world as we know it now in North America. The
main ice sheet that we have that is in this part of the world is the Greenland
Ice Sheet. What was left from a much larger ice sheet is now this little
Barnes Ice Cap on Baffin Island up in Canada here but that was once a large
ice sheet here we call the Laurentide Ice Sheet and this big thing that came
all the way down here: Chicago was under ice, New York City was under ice, a lot of
Minneapolis, a lot of our upper tier of states/ large cities were all under ice,
virtually all of Canada as you can see here, and here in the western part of
North America we had another Ice Sheet called the Cordilleran Ice Sheet. Wasn't
as thick or as big as the Laurentide Ice Sheet but still not not trivial
either. and so we've got a whole lot of ice here and we had a larger Greenland
just for good measure and our mountain ranges in Alaska had bigger glaciers
plus over in Eurasia we had the Pentoscandian Ice Sheet as well. Where did
all that water come from? There's only one place it can come from and that's from the
oceans. So air masses that would come across and fall as snow here in the
northern parts of Canada and farther to
the east in the northern parts of Eurasia
during a cold climate so that the snow would stay over through the summertime
into the next winter kept building up building up building up building up
building up building up pretty soon you get to the point where a certain
critical density is reached then flow on its own weight and you've got a glacier-
you've got an ice sheet. okay. That's what we have right now in Greenland, a little
bitty one here at the Barnes Ice Cap which characterized the upper part of
North America during the last ice age and in all previous ice ages and there were
more than 20 of them over the last two and a half million years. So if all of
that moisture to build that ice sheet came from the oceans what's going to
happen to sea level? It's going to go down. okay. all right. So what we see then
in a place like this part of the world is enormous amount of land area that
extends out from our present coastline and you see it right here going from the
stunning metropolis where I grew up called Lompoc- it's actually a really
nice town, not a stunning metropolis but it's a nice town- and at any rate all of
this white area that you see here is the land that would have been created around
the mainland as sea level dropped and reached its maximum during the last
glacial period about 20,000 years or so ago. Well out here in the Channel Islands
look what happens there's a lot of shallow shelf surrounding the islands
and all of that gets exposed as land and all four islands get connected into one
big island that was dubbed Santa Rosae by Phil Orr of the who at that time was at
the Santa Barbara County Museum. Now depending on which sea level histories
you look at, the actual area that or the actual depth to which sea level drop
could have been as high as 95 meters or as low as 120
meters, it turns out it's not exactly the same on each coast because there's other
other, excuse me, other factors involved which I won't get into but either way
you're looking at a significant increase in land area with all these islands being
connected. So now what's our distance to the former ice age Oxnard: 7.2 kilometers,
okay, not nearly as much, still no land bridge though. how they gonna do it?
This is the way they're going to do it. It turns out my undergrad adviser and
masters advisor at the University of Illinois who was a native Californian
and who worked on the Channel Islands the one who named the caliche forest was
fascinated with mammoth, fascinated with biogeography, and was trying to address
this question because he knew these landbridge theories were wrong, couldn't
possibly be true. He knew the geologic and geophysical evidence was against it.
So he started looking through- this was back in the in the 60s now and early 70s-
started looking through accounts of elephant behavior- modern Indian and
Asian elephant behavior- and seeing what people had done and they observed how
they interacted with their environments and so on and discovered there were a
number of cases of elephants swimming. Sometimes forced swims, for example
during an ocean-going ship having an accident at sea and then a an elephant
getting loose and then for its own survival swimming to shore as much as 30
miles one way which would be about 45 kilometers. (laughter) so there! okay pretty good huh?
And so at any rate that was a forced swim but voluntary swims have been
documented as well and it turns out elephants are excellent swimmers and
both Indian ones and African elephants and a lot of their relatives like
manatees so closely related too, okay, and the stellar sea cow. Anybody heard of
the stellar sea cow? They're not around anymore but they were around not so
long ago, they certainly were swimmers; related
vaguely to elephants am I correct? yep, okay, good, I'm on track. And here's a good
example right here: Rajan, the swimming elephant of Havelock Island, India. This
poor guy had had some troubles earlier in life as you can see and had a lot of
cruel activity placed on him but has been adopted by the residents of this
island. They take care of this guy and every once in awhile he goes out for a swim
and does this voluntarily, has a great time, uses his trunk as a snorkel, and a
way he goes. So my old advisor documented this before Rajan was born actually. The
Origin of the Island Mammoths and the Quaternary Land Bridge History of the
Northern Channel Islands, California. He came up with the mechanism. Finally
explained why we had elephants- mammoths, that is, their cousins- out on the Channel
Islands but no other large mammals and you don't need a land bridge to explain
it and he also added to this the evidence of why they went out there he
actually looked at some of the buried sand dunes that were cemented it had
their dip angles which tells us what the wind direction was, demonstrated that the
winds were westerly just as they are now with a lot of lush vegetation out there
that comes wafting across. These guys can smell this and they say hey there's a lot of
good eating out on those Islands let's go swimming, that's what they did. ok. now
what happens when you end an ice age though? What happens to sea level? All
that water goes back in the ocean, sea level goes up, and all the sudden they're
stranded ok and this is when we start to see some of the kind of dwarfing process
sometimes take place. So what I'm going to show you here this looks very
complicated but it's actually not and it's easy to to walk you through it. What
this is is basically a sea level curve or ice ages and interglacials that are
in between them. We call the periods in between ice ages, like the one we're in
now, interglacials. And this is time on this axis in thousands of years so
that's a 100,000 years, 200,000 moving back to about 450,000 years here
so every time you see a high point we're in an interglacial and sea level is high
okay. And every time you see a low point you're in a glacial period and sea level
is low so this is essentially how the ocean is going up and down and up and
down and up and down and up to our present level so during the last glacial
period when all that ice was covering North America we were in this low point
right here and you can see that last glacial period was one of the lowest of
the lows of the last few hundred thousand years so it was a big big
glacial let's say. And these different cycles here are given numbers I've shown
the interglacials in red and those are called stages so this is stage one that
we're in and so the last glacial period would have been stage 2 you know the
most recent of the glacial periods. So what we see from, well, the photos I've
shown you already are a lot of stage two aged mammoths okay and we don't have any
stage one age mammoths on the Channel Islands, we haven't found anything younger than
about 12,800, does that sound right? okay so we're really sort of at the tail end of
the stage two at that point but we have these earlier glacials as well and
although they weren't maybe quite as dramatic as the last one maybe this one
was pretty close they're still not insignificant and they are still thought
we're still talking about fairly low sea level and land masses of the Channel
Islands that would have been closer to that big landmass of North America.
So we're going to take a look at this last part last sort of glacial-
interglacial-glacials cycle right here in a bit more detail so we're just going
to take that part of the curve and expand it out a little bit here. So here's the
last interglacial this was a period of time when sea level was actually higher
than it is now and we see evidence of this in places
like the Florida Keys. Florida Keys are all coral reef material in their upper
part that is a coral reef that records six meter higher level sea compared to
the present one. Same thing in Hawaii the Waimanalo formation is a coral reef
limestone and most of the city of Honolulu is built on it. okay. So during
the last interglacial, Honolulu and Key Largo would have been underwater and so
would Miami and St. Petersburg and Cape Canaveral and yep Disney World too okay.
Disney World might be underwater pretty soon I'm sorry to say. At any rate so
that's our last interglacial, and it was a whopper, it was a sea level was much
higher and it was much warmer than it is now and we'll return to that theme too.
Okay that's stage 5 E: this whole period in here was our stage five in the last
graph, we've actually sub divided it into three sub stages here, E, there's a D there,
C, a B there and a A here. Clever huh? Scientists have learned the
alphabet! okay. all right. And then we have an early last glacial and then a little
start of an interglacial that kind of fizzled and then we go into stage two
which is our big last glacial state going into the present interglacial. Well most
of our mammoth radiocarbon ages fall into stage two there's a few that are a
little bit older but at this point when we get into 35 to 40 thousand years a
lot of our radiocarbon ages are not necessarily reliable just a small amount
of contamination can make what is an infinitely old age appear to be an age
of about 30 to 40 thousand so we have to treat those kind of cautiously
but it does indicate something older than the last glacial period okay or
stage two but that's what our majority of our ages are. So the question is, well
gee, if we had all these earlier glacial periods could there have been earlier
migrations? And actually good old Don Johnson hypothesized this as well when he
was describing the whole sequence of last glacial migration by swimming he
said possibly this scenario occurred several times during the Late
Pleistocene (meaning the ice ages) so this is something he recognized could have
happened anytime sea level was low enough that the distance was shortened
between the islands and the mainland that it was within swimming length. okay? So we
always wondered about this and we were always curious about it and we're always
thinking, gee could we ever find some geologic evidence of earlier migrations?
And actually there was a clue that was given by Phil Orr, guy who named Santa
Rosae for that ice age mega island in 1960 and he was talking about Santa Rosa
Island and he was talking about one of the uplifted marine benches that marks a
high sea level stand; no it's not like Hawaii like Honolulu or Key Largo where
the land is not going up; here in California the land is in many places
slowly uplifting and the Channel Islands are among those so when we get a marine
bench during an interglacial high sea stand, with time it gets lifted out of the
water a little bit, and if you've ever driven along most of California Highway
1 from here all the way up to San Simeon you're driving on that last
interglacial bench that's been uplifted out of the water. okay? how about that? So
anyway what he whoops, sorry, what he said was he was describing some of these
marine deposits in one of these terraces "in general a light gray calcareous clay
containing fossil bones of whales, sea lion, sea otter, shorebirds, and occasional
dwarf mammoth." Whoa! That means you're talking about a dwarf mammoth that has
got to be beyond radiocarbon age and goes all the way back into some part of the
last interglacial complex because that's the age of the deposit he's describing.
okay. So we thought well let's go look at these sorts of deposits and see what we
can find, are there occasional dwarf mammoth fossils there. So we were doing the
mapping of marine terraces on Santa Rosa Island over the last few years. These
brown areas that you see here are some of the old ones these go back sometimes
millions of years not many millions but a couple millions of years but around here
this whole light, more yellowish color is the complex of one or two terraces that
represent those stage 5 high sea stands, you know the 5 E, 5C, 5A, those in that, excuse me, those
in that time period are all along the shore there on Santa Rosa. This is what
they look like: it looks like just a sort of a flat bench, a Mesa-like one, the upper
higher Mesa that you see here is an older marine terrace or terraces but in
this canyon our exposures of what you'll see is a wave-cut bench that's got fossils
on top of it, the sea shells in there that date to the last interglacial, and they're
the same species that we find living on the modern coast today. There hasn't been that
much time that they've changed or evolved that much but this is what they look
like so what we do is we scour exposures and canyons like these and along sea
cliffs like these to see what we can find in there and we were doing this
collecting these for fossils to try to date these and they once you get in the
canyons they look something like this: this is one of those wave cut benches
right along in through here that I've outlined. This is shale which is millions
of years old and you can see there's an old sea cliff that's been cut and
there's a wave cut bench that's been cut. And this is a wave cut bench of a higher
terrace and then there's been river deposits from this canyon that has
buried all of this. But right along here I want you to trace that along that wave-
cut bench. That's from the 80,000 year old terrace and all the
way out to this sea stack out here, we're going to go out there. And this is what
it looks like when you look close up: there's that shale again. This is in a
nice low tide. This is the Rincon Formation, the shale, millions of years
old. But look what we've got here, we've got a wave-cut bench and there's a layer
of boulders that are the sort of boulders that you find sitting on the
beach over in here, along here, today. They have little holes
that have been bored by rock mooring clams, there's fossils in there, sea otter
remains, and we're going to look right here... and guess what we found. A tusk! How about
that? There it is. There's a tusk. And I sent a photograph of this to Larry Akenbroad
because I had been sending him photographs for years saying I think I
found a tusk, I think I found a tusk,and I'd sent him a picture and he'd say that's a
whale rib Dan and/or would say that's a large root cast Dan and there are all
kinds of things that I misidentified in my enthusiasm but this time he wrote
back right away and he said you've finally done it you found a pygmy mammoth.
So there it is okay. So here's our Rincon shale, really old, that's the
bedrock, its wave- cut benches, this boundary right through here, and within
this deposit one of our cohorts at the LA County Museum, Lindsay Groves, found
these limpets and other marine gastropods or snails if you will so we
know that's that's marine material and Howell Thomas, his vertebrate
paleontology sidekick, also at the LA County Museum found enough fragments he
was able to actually identify this as a sea otter with these bone fragments and
it could even take it down to the species. ok. now. It's easy to get
terrestrial fossils mixed into marine fossils because all you got to do is
erode them out into the ocean. ok. So on a sea cliff you know all you got to do is
have a mammoth who's walking along the top near the cliff slips, or dies
naturally, or something, falls into the surf zone everything gets eroded
together in with these marine fossils and you know this can happen. It's
tougher for marine fossils to get up onto the land because they have to defy
gravity to do that. ok. And not too many of them do that. They you know celebrated
Jumping snails of Ventura County have never been verified so at any rate so we
know that this is a bona fide marine depot
and this is a mammoth tusk that was washed into it now it's interesting
about this when you look at the dimensions of this thing, this puts it
sort of into the range of either a pygmy mammoth or truth be told it could be an
immature Colombian mammoth. we really don't know for sure, but it's one of those
two. It's no question it's a mammoth tusk for sure within these marine
deposits. So I should say this is probably a pygmy mammoth. But at any
rate, when could mammoths have migrated to the Channel Islands? This marine deposit
it was found in is right here so it's within stage five... that's five E, C, A...
this is 80,000 years old okay, all right, Now because it's 80
thousand years old or in a deposit that's 80,000 years old that means it's at
least 80,000 years because it had to exist before that marine deposit
was created. Could be right at 80,0000, or close to it but it can't be any
younger okay. So you can't have that sort of a situation in geology or you're
violating the rules of geology, no one wants to do that. So we know it has to be
at least 80,000 years old but could be older. Well when did it or its
more likely its ancestors migrate over to the Channel Islands? Well if you look
at Stage 5 B here, sea level wasn't really much lower than it was during
these high sea stands. 5C was not very low, 5D wasn't very low and we know 5E,
that's when Hawaii and Key Largo and Miami and all those places were
underwater so sea level was much higher right. So you're talking about swimming
distances that are comparable to what we have now or were even greater, okay. So when's
the most likely time, how about stage six okay, how about stage eight, how about
stage 10. Any of those glacial periods are candidates so we know then that mammoths
migrated to the Channel Islands sometime before the last one during stage two so
we know there had to be at least two migrations, at least two,
maybe more we don't know. okay. So how does that play out? Well if you look at a
cross section of Santa Barbara Channel the mainland and the islands out here
and these are those marine terraces that I showed you the picture of on Santa Rosa
these wave cut benches. okay. They've been forming the last 20 million years on the
California coast as we've had glacial- interglacial cycles and we hit a high
stand to sea and then sea level drops during a glacial period and the land
uplifts and the terrace gets run out of the water. Well this is going on on
the islands and it's going on on the mainland so the channel distance here
used to be greater in the past before all this uplift took place and then
through time it's been shrinking so maybe eventually we will get that
island who knows okay you gotta you know bring it up to 240 meters depth so
that's that's maybe not going to happen for a while yet. At any rate there was a
time probably when this distance was actually beyond the range where mammoths
could swim. Just too far. And maybe even during the next low stand of sea, or
glacial period, it might have still been too far. At some point and we don't know
if it was stage 10, stage 8, stage 6 or even some time earlier but some point
sea level got to the point where it was low enough and uplift had taken place on
the land and on the islands to a sufficient extent that this distance was
short enough for where they were finally close enough they can swim across. And then
when we get to the last glacial period which was this whopper okay, sea
level really dropped, and enough uplift had taken place, the channel was down to
that short distance of seven kilometers or so and easier to swim then even
before and away they went and that's where we see a lot of the mammoths that date
from the last glacial period, both Colombians and pygmies. Now we don't know
whether those pygmies evolved during the course of the last glacial period or
from the earlier migration, you just don't know, so this is something that
Monica and Justin will tell us about when they get all done with their stuff,
right? yeah, that's right, that's the spirit, that's that can-do spirit in the
mammoth community. But here's another question: why did they become extinct? And
there is probably no subject in Pleistocene paleontology more
controversial than how the large mammals of North America, Eurasia and Australia and a
lot of other places became extinct at the end of the Ice Ages. And it's
variable. Some became extinct sooner than others and it turns out actually some of
them nearly escaped. There were mammoths on place called Wrangel Island off the
northern coast of Siberia that existed there until 3500 years ago. Isn't that amazing?
They almost made it, almost made it. So when the pyramids were built there were
still mammoths on the earth. Isn't that amazing to think about? So I feel sorry for those
guys they almost made it and not quite. Anyway we know from the geologic record
on the Channel Islands that mammoths became extinct on the Channel Islands
somewhere around 12,000 years or so ago and perhaps just a little older or something
on that nature okay at the end of the last glacial period. There have been
three major hypotheses that have been presented. One is impact from an
extraterrestrial object- a comet or meteor- and this is an idea that has come
into vogue just recently. There are a lot of people that have kind of gone along
with this concept and I'll talk a little bit more about it here in a second. A
more favoured hypothesis is climate change and sea level rise when we
shifted from a glacial to an interglacial climate so that conditions
were warmer, there would be a loss of land area so that Santa Rosae would start
to break into individual islands okay. All of a sudden you got less land area,
less in the way of food resources, and so on. And this idea is favored by a lot of
people. Here's another one that's favored by a lot of people that's the arrival of
humans could be very close to the time when the first humans were arriving on
the Channel Islands okay, within a couple hundred years in fact,
within our uncertainties with radiocarbon dating. So let's take a look at
each one of these. That first one, this has been controversial to say the least.
Here's one of the groups that has come up with this. They came up with the idea
that this large celestial body impacted on the surface of the earth, brought
about all kinds of things: wildfires, ecosystem disruption, the creation of a
cold period that's referred to as the Younger-Dryas, this was a brief period,
we know this did happen, this cold period, a brief period where we were
moving out of the last glacial period, the last ice age, into the present
interglacial and then suddenly we had a precipitous drop in temperature globally,
or much of the globe anyway, lasted for a full 1000 years and was near glacial
conditions. More glaciers that actually re-advanced in the mountains in
Colorado where I live, and this has been verified and we see it in a lot of geologic records
and this was also about the time that a lot of these large mammals became extinct. So
these guys are saying that all of this was caused by this impact event and
they've accrued a lot of evidence that they present in support of this
hypothesis. And then there are others that are the doubters to this theory. In
fact they've been rather blunt about this, they have assembled all the
evidence against it and actually refer to this as a requiem so so you
don't see this kind of terminology in a lot of scientific literature, usually we
try to be a little more restrained and you know. But this is amounting to saying
you know well you guys are you know full of it here and but in truth these guys
have worked hard to try to come up with supportive evidence for this, these guys
have also worked hard to evaluate that evidence and quite honestly my feeling
is that these guys are probably more closer to the truth than these guys are.
The jury is still out on this but most of the evidence suggests a lot of the
evidence that these guys used is questionable or can be explained in
other ways. So we're going to leave it at that. I'm
not going to get into this one because it's quite a quite a mess with the back
and forth on that but we're just going to say not likely not likely, not not no,
but not likely. So climate change and sea level rise when we shifted from a glacial
to an interglacial climate, that is possible. Here's one problem. Remember we
said that the mammoths had to come over at least twice, right. Once during the
last glacial period for sure, we know that, we see plenty of evidence of that.
And at some favorable glacial period prior to that, sometime prior to 80,000
years ago, we don't know when, could be stage six 150,000 years ago, stage eight 250,000
years ago, so we don't know when, but one of those periods when sea level was
low. Remember I said too that the last interglacial period when sea level was
higher that it would have been after that migration took place whether it was at
250,000 years ago or 150,000 years ago both of those are prior to the last
interglacial when conditions were interglacial-like 120,000 years ago.
Okay well in a lot of places in California Southern California where
these red dots are showing up here we have records of not only a higher sea
level and then uplift but also the marine invertebrate fauna within that,
all the snails and bivalves or clams and other organisms that are in there, tell
us that the waters around here were a lot warmer than they were during the
current interglacial so things were not sea level is not only higher but
waters were warmer probably had more El Ninos or they had a lot of things that
now live in Baja California or Central America migrating up in the Santa
Barbara Channel so conditions were a lot warmer. Furthermore you even see it in
fossil pollen that's recorded in a core that Jim Kennedett at UCSB took right out
here in the deepest part of the core that indicates that the vegetation tells
us it was a much warmer climate as well. So if sea level was higher
and conditions were warmer then that means we actually had, this is the last
interglacial shoreline right here along these islands where it's still preserved
and not all the places but you can see they're all inland because sea level was
higher right so what does that mean about these island sizes. They're
actually smaller than they are now okay a sea level was higher all right and the
waters around here were warmer and then what did we move into. The first part of
the glacial period right and then we had a little, remember, a little failed
interglacial period and then we moved into the deep last glacial period. So
mammoths then survived, came over during some glacial period, survived the warmest
interglacial of the last 400,000 years and then a glacial period that started,
and then a half started interglacial period, and then one of the
coldest glacial periods, and then they moved into a rather modest interglacial
the one that we're in now and then they decided that they had to die because
they couldn't survive anymore? Doesn't make sense because they survived an
interglacial that was more intense than the present one and where the land area
was smaller than it was at the end of the last glacial period and all the
islands broke up again. So not only did the old Santa Rosae break up into
islands, they were smaller islands than they are now, and somehow they did okay.
They survived because they we see them all the way to the last glacial period.
That's the problem with the climate change hypothesis okay. Not the idea that
the idea isn't that it's totally wrong or anything like that, but it's a problem
with it, ok. Now another possibility is the arrival of humans. That is also
possible. And one of the things we've learned in studying mainland North
America is that there are a number of places where there are bona fide mammoth
kill sites, ok. Now there are claims that there are a lot more of them and some of
them are equivocal, all the ones that you see here in the little black and white
dingy colors are kind of supposed evidence of large mammal kill sites but
these are all ones that have been compiled by these two guys who are
skeptics about the idea that humans were responsible for the demise of large
mammals at the end of the last ice age. But even with their skepticism they
agree that there are some genuine sites where there's good archaeological and
paleontological evidence that there were kill sites specifically for mammals. So we
know it's not a question then of saying well gee humans couldn't have been
responsible because we just can't believe they would kill mammoths. That's not
true; we know that they did, okay, the evidence is there. But what we haven't found
is a kill site on the Channel Islands, no one has ever found it. There were claims to that
effect back in the 60s and those have all been debunked okay. Turns out a lot
of those were reported to be hearts and actually places where mammoths were
barbecued by by humans living on the islands at that time. It turns out they
are burn sites but they are from naturally occurring fires okay so we can't count
those. So it's true we do not hit whoops... we do not have any bona fide kill sites
on the Channel Islands as of yet but we do have them elsewhere so this remains a
possible hypothesis as well. Here's I think the one that I kind of favor and
that is.. okay we're not going to go with the impact idea, we're not going to go
with climate change alone, we're not going to go maybe with arrival of humans
but keep open that possibility, but how about climate change AND the arrival of
humans. Now that's a double whammy. Okay when you change climate, you diminish
resources and then you have these strange creatures arriving. All of a
sudden you've got a totally different mix of variables in an animal's survival,
okay. The jury is still out on actually on all four of these hypotheses. I don't
have a strong feeling about any one of them. If you backed me into a corner with
a gun and said you must commit to one or the other I'd say I can't okay it's not
really we're not at that state but I'd put my
money on this at this point probably this combination. Anyway, so summary.
Mammoth remains are found on the Channel Islands and most date to the last
glacial period. They reach the islands by swimming during a glacial period when
sea level lowered and the mainland to island distance was at a minimum whether in
English or metric units. It has been hypothesized that mammoths could have
made the swim more than once prior to the last glacial period and we recently
found a mammoth tusk dating to 80,000 years. This older
age requires a pre-last-glacial period migration it was probably during
an earlier glacial period, we don't know which one. But even during glacial
periods, uplift has to bring the islands and mainland close enough for mammoth
migration and we don't know when that occurred. Mammoths survived a warmer last
interglacial period but climate change and the arrival of humans at the time of
climate change may have brought about extinction of the mammals. We don't know,
that's still a hypothesis that needs more testing but we'll see what the
mammoth world tells us in the future. thank you very much. (clapping)
Questions? (mumbling) Actually Bryson here is going to give you a microphone so everyone can
hear your question. You were saying there's no geologic evidence for the
land bridge and was that primarily because of the depth of the water and with the
changing sea level there's no way that that... That's part of it and also, that's right,
that's part of it and some of it is just geologic evidence of you know matchup of
rock types and things like that and geophysical evidence which I'm not an
expert on so I can't evaluate but I took it from people I trust that there's
there's good evidence against that and so on. So it turns out all the land bridge
ideas were all constructed on the basis that because there were pygmy mammoths
out there they had to get out there by traversing land and not by swimming so
land bridge idea never had any geologic evidence all it had was paleontological
evidence, and it turns out we have another mechanism. And I've got one other quick
question, so on the kill sites yes for the mammoths where so it was established that
these areas where you identified the kill site truly showed that it was a
human yes where you could show where there was cut marks or whatever on the remains so
definitely human? Yeah and these two guys particularly Dave Meltzer who is a good
friend of mine teaches at Southern Methodist University he's a very very
careful archaeologist and very cautious and conservative in how he interprets
things and his passion is the earliest arrival of humans in North America and
so he's aware that there have been throughout, well past few decades but
for a long time claims of early human migrations to North America you know
going back 100,000 years, 200,000 years just incredible
claims and he's been very skeptical about all is and he's done a lot of the
debunking of what were in some cases some pretty poor
accumulations of evidence so when you look at this and see those sites that he
agrees are actually human, you're looking at one of the most critical eyes. He's actually
looking to eliminate sites and these are ones that he agrees those are genuine
kill sites, so there's about a dozen of them, there might be more by now.
Justin and Monica do you know? More mastodon sites yeah. I didn't put the mastodon
sites up there, at the time they wrote this paper there were at least two
mastodon sites, and I think, sounds like there may be more than that now. Yes
that's right but I wanted to keep it to the mammoths so that was the reason for
that. Dr. Muse isn't there... is it on? yeah. it was there not evidence that both
Colombians then pygmies were coexisting there for a later period? Yes I'm glad you
asked that I was hoping someone would ask that and I should have mentioned it.
Yes based on the radiocarbon ages that actually Larry Akenbroad had gotten
for a number of the sites on Santa Rosa Island there's good evidence that we had
both Colombian and pygmy mammoths out there at the same time at least roughly
at the same time you know within a couple thousand years or what our
radiocarbon dating allows us to try to delimit. Now the site that Justin and
Monica have worked on here has some interesting characteristics about it
with regard to this issue. Now the idea is of course that if you have the
islands here the mainland here the Colombians swim out and land on the
islands, the big guys start dwarfing/ evolving down two little ones, we get a
small population, okay, and if you have further migrations before sea level
rises then you could have Colombians and mammoths coexisting, or if you had two
migrations or more you could have Colombians migrating out, they all dwarf
down to pygmies, and then during the next glacial period
they migrate out again and you've got pygmies and Colombians together. Now the
fact that we see pygmies and Colombians together during the last glacial period
doesn't mean that that all the dwarfing took place just during the last glacial
period but doesn't exclude that possibility. So it's possible that some
of the pygmy remains we found out there that are from the last glacial period
are actually the ant the descendants of earlier migrations and then the
Colombians are the recent arrivals but then some of them could have also dwarfed
quickly. We don't know how quickly the dwarfing process takes place. One of the
things that Don Johnson hypothesized was that if they did evolve from Colombians
to pygmies over an extended period of time or even rapidly there should be
some geologic evidence of some intermediate sized critters, right. That
makes sense because it doesn't happen instantly you know. So Justin do you want
to make a comment about that or Monica do you want to make a comment about that
with your recent find? there you go! okay. We don't know what that means yet and these
guys are going to study it but what's interesting is it, correct me if I'm
wrong Justin, this is one of the first bona fide finds where you could actually
make you have enough evidence that you could actually make some kind of a
statement than it looks like it's kind of intermediate as a possibility. right.
right. so. yeah. So here's the thing to do. These guys are going to be working on
this skull that they found, this possibly intermediate-sized thing, and at the
Santa Barbara County Museum they'll be coming to California periodically. Most
people would prefer to stay in South Dakota in the wintertime where they live
but we've managed to entice them into thinking of coming down here and so
they'll be doing things and I as I understand it there might be in the
future some exhibits at the Santa Barbara Museum where some of this work
will be taking place and so watch for notices from Santa Barbara Museum
Natural History and Cherry Carlson who has been following the mammoth research
with the Ventura County Star might have an article about this every now and then
in the VC Star so keep your eyes open for for that as well she's become a real
mammoth aficionado so she's been following all the work that everybody's
been doing here very closely and done a good job recording it so if news comes up
on this she's going to tell you about it. So anyways does that answer your question?
Yeah, okay. We have time for one final question here tonight. Okay. I think you're
first and... I'm first I have the mic. Ok. Whose first? I'm back
here in the back and I've got the mic okay
I pretty much put you in the driver's seat. yep you got it. yeah my question is,
I've heard that the mammoths didn't do well when islands were individual as
opposed to when it was Santa Rosae and there were more flat area that they that
mammoths as a whole just don't you know they don't do well in mountainous
terrain where there's a lot of topography. Oh well actually what happens
is these islands get more topography as time goes on so in the past they
actually would have had less topography they would have been flatter
because it wouldn't have been uplifted as high and so I don't think that would
have been a limiting factor quite honestly. What would have been more of a limiting
factor is the shrinkage of those islands for sure, because you lose land you'll
lose the foods resources that are on that land. That would be way more
important. That's true, you have rougher terrain, yeah that's true enough. On the
other hand because most of these islands have been constructed by slow uplift of
these marine terraces which are by their nature flat features you still would
have had a fair amount of fairly flat terrain it just would have been reduced
in size. So the amount of area I think would probably even more of a factor.
Yeah. There are some questions up front here yeah would you like to answer I think this
woman was first and then right over here this gentleman. During the time that
humans begin inhabiting the islands can you talk to us about maybe the number of
mammoths that would have been on the islands at the time. Oh my. Do you know? What
do you guys think, Don, Justin, Monica? This is really hard to tell. yeah. yeah.
I can give you a ballpark it less than present-day Los Angeles, no doubt about
that. I'll stake my reputation on that. Over here, sir. I don't remember the exact
date but I think it was like 120,000 years ago, the water
level was much higher? yes that's right. Got it. What was got cause for that rise?
Ah this is near and dear to my heart. Surely it was before the Industrial Revolution right? Oh yeah.
Few years before yes the we think there's been a lot of debate about this.
Six to eight meters higher you can do it with one Greenland, one West
Antarctic Ice Sheet plus part of Greenland, or all of the West Antarctic
Ice Sheet and a bigger part of Greenland's. All the other little ice
caps and things like that that we have now would would not amount to much more
than about a half a meter. The best evidence we have so far is that about
two-thirds of Greenland went away during the last interglacial period so that
gives you about let's say four to five meters. To make up the rest you had to
get rid of all of the West Antarctic Ice Sheet. So the thinking is that it was
probably most of Greenland and all of the West Antarctic Ice Sheet at that
time now to get to get six to eight meters. yeah oh no no no no no no no no
I'm sorry. I thought you're talking about meters in terms of measurements no okay
yeah yeah no no no no. This is that whole cyclicity that you see there is due to
changes in the Earth's geometric relationship with the Sun and the amount
of solar radiation that reaches the northern hemisphere in summer okay.
Because remember we said that the you build up a glacier in that part of the
world by having conditions cool enough that the snow that falls in the
wintertime stays over in the summer into the following winter and when you keep
repeating that again and again and again and again you start to build up a
glacier. One of the ways you can do that is if you diminish the amount of solar
radiation reaching that part of North America and Eurasia in the summertime
due to changes in three things. One is the ellipse.... the whether the Earth's orbit
around the Sun is more elliptical or more circular, that has a 100,000
year cycle. Whether you have a precession of the equinoxes because they
due precess the way a top does so that at times we have, like right now, our
northern hemisphere winters occur when we are closest to the Sun but we're
tilted away from it okay. There are times when our northern hemisphere winters
occur when we're farthest from the Sun and we're tilted away from it so you
have colder winters, warmer summers. And then there are changes in the Earth's
axial tilt okay we're presently twenty thank you we're presently 23 and a half
degrees away from vertical but it varies from about 20 to about 24 okay. When all
of these things combined in such a way and those we have a 100,000
year cycle, 40,000 year cycle, and a 20,000 year cycle. When all three of those
things combined you have very little solar radiation reaching northern
latitudes in summer for extended periods of time you get ice ages
initiated okay. And then when the reverse happens and you have a maximum amount of
solar radiation in northern hemisphere summers they all melt and we have
interglacials okay. Now the way that these all vary is due to the other
planets and our relation to them, the gravitational effects they have on them
and this is all done by computation and celestial
mechanics. It's mathematics that I do not even attempt to try to understand. But
it was hypothesized long ago, it's well-established now as one of the main
drivers of the ice ages and interglacials in between and that's
probably a longer answer than you wanted but that's the main driver behind it.
Alright we have time for one final question. okay. I'm wondering how did the
paleontologist know where to look? For example with the latest find how did
they know where on the island to look for this skull and my second question is
do you know approximately how many years humans and mammoths were coexisting on
the islands? I'll answer the last one first and then I'll defer that other one to
the mammoth paleontologists. We we don't know that they did coexist. All we know
is that the radiocarbon ages of the earliest humans and the latest mammoths
are getting very close to one another within our analytical uncertainties but
they are uncertainties okay. So we do not have bona fide evidence that they were right
there at the same time. And what hope everyone goes away with that
understanding. We don't know for sure; all we know is that it is possible, we don't
know for sure. So that's Part B. Part A: how do you find a mammoth skull?
Everybody here now we we look at the geology that Dan puts together and then
we go out and we scour those places that are likely to have dirt of the right age
okay alright and then we look in that dirt. Now for a Mammoth's skull we cheat. We
have Park interns go out and then they report what they see.
But no oftentimes the paleontologist isn't the person that finds the specimen.
It is he or she is the one that goes out, documents, excavates, and tells you what
it's in, and what it means. A lot of it is just keeping your eyes open when
you're out doing other things and in fact that this particular mammoth find
was discovered by a guy named Peter Leraman who is an ornithologist and who
was walking the canyon and saw this and said mmm and it went from there. So a lot
of these discoveries are made by serendipity and a combination of
serendipity and people who have their eyes open and are thinking about what
they're seeing so that's that's the business model for mammoth hunting so
okay alright think we're done. Thank you.