TPO 9 Lecture 3
Geology
Lecturer: So, continuing our discussion of desert lakes, now I want to focus on
what's known as the "Empty Quarter". The "Empty Quarter" is a huge area of
sand that covers about a quarter of the Arabian Peninsula. Today it's pretty
desolate, barren and extremely hot. But there've been times in the past when
monsoon rains soaked the Empty Quarter and turned it from a desert into
grassland that was dotted with lakes and home to various animals. There were
actually two periods of rain and lake formation: the first one began about
35000 years ago; and the second one dates from about 10000 years ago.
Female Student: Excuse me, Professor. But I'm confused. Why would lakes
form in the desert? It's just sand, after all.
Lecturer: Good question! We know from modern day desert lakes, like Lake
Eyre, South Australia, that under the right conditions, lakes do form in the
desert. But the Empty Quarter lakes disappeared thousands of years ago.
They left behind their beds or basins as limestone formations that we can still
see today. They look like low-lying, white or grey builds, long, narrow hills with
flat tops, barely a meter high. A recent study of some of the formations
presents some new theories about the area's past. Keep in mind though that
this study only looked at 19 formations. And about a thousand have been
documented. So there's a lot more work to be done.
According to the study, two factors were important for lake formation in the
Empty Quarter: first the rains that fell there were torrential. So it would've been
impossible for all the water to soak into the ground. Second, as you know,
sand dunes contain other types of particles, besides sand, including clay and
silt. Now, when the rain fell, water ran down the sides of the dunes, carrying
clay and silt particles with it. And wherever these particles settled, they formed
a pan, a layer that water couldn't penetrate. Once this pan formed, further
run-off collected, and formed a lake.
Now, the older lakes, about half the formations, the ones started forming
35000 years ago, the limestone formation we see, they're up to a kilometer
long, but only a few meters wide, and they're scattered along the desert floor,
in valleys between the dunes. So, the theory is, the lakes formed there, along
the desert floor, in these long narrow valleys. And we know, because of what
we know about similar ancient desert lakes, we know that the lakes didn't last
very long, from a few months to a few years on average. As for the more
recent lakes, the ones from 10000 years ago, well, they seemed to have been
smaller, and so may have dried up more quickly. Another difference, very
important today for distinguishing between older lake beds and newer ones, is
the location of the limestone formations. The more recent beds are high up in
the dunes. Why these differences? Well, there are some ideas about that, and
they have to do with the shapes of the sand dunes, when the lakes were
formed. 37000 years ago, the dunes were probably nicely rounded at the top,
so the water just ran right down their sides to the desert floor. But there were
thousands of years of wind between the two rainy periods, reshaping the
dunes. So, during the second rainy period, the dunes were kind of chopped up
at the top, full of hollows and ridges, and these hollows would've captured the
rain right there on the top.
Now, in grassland of Lake Ecosystem, we'd expect to find fossils from a variety
of animals, and numerous fossils have been found at least at these particular
sites. But, where did these animals come from? Well, the theory that has been
suggested is that they migrated in from nearby habitats where they were
already living. Then as the lakes dried up, they died out. The study makes a
couple of interesting points about the fossils, which I hope will be looked at in
future studies. At older lake sites, their fossil remains from hippopotamuses,
water buffalo, animals that spend much of their lives standing in water, and
also, fossils of cattle. However, at the sites of the more recent lakes, there’re
only cattle fossils, additional evidence for geologists that these lakes were
probably smaller, shallower, because cattle only use water for drinking. So
they survive on much less. Interestingly, there are clams and snail shells; but,
no fossils of fish. We're not sure why. Maybe there is a problem with the water.
Maybe it was too salty. That's certainly true of other desert lakes.
TPO 9 Lecture 4
Linguistic
Listen to part of a lecture in a linguistics class. The professor has been
discussing Animal communication systems.
L: OK, so last time, we covered the dances honey bees due to indicate where
food can be found and the calls and sounds of different types of birds. Today,
I'd like to look at some communication systems found in mammals, particularly
in primates, such as orangutans, chimpanzees, gorillas... Yes, Thomas?
T: Excuse me, Professor. But when you talk about gorilla language, do you
mean like, those experiments where humans taught them sign language or a
language like...
L: OK, wait just a minute. Now, who in this class heard me use the word
"language"? No one I hope. What we're talking about here, are systems of
communication, all right?
T: Oh, sorry, communication, right. But could you maybe, like, clarify with the
differences?
L: Of course, that's a fair question. OK, well, to start with, let's make it clear
that language is a type of communication, not the other way around. OK, so all
communication systems, language included, have certain features in common.
For example, the signals used to communicate from the bee's dance
movements, to the word and sentences found in human languages. All these
signals convey meaning. And all communication systems serve a purpose, a
pragmatic function of some sort. Warning of danger perhaps or offering other
needed information. But there're several features peculiar to human language
that have, for the most part, never been found in the communication system of
any other species. For one thing, learn ability. Animals have instinctive
communication systems. When a dog, a puppy gets to certain age, it's able to
bark. It barks without having to learn how from other dogs, it just barks. But
much of human language has to be learned from other humans. What else
makes human language unique? What makes it different from animal
communication? Debber?
D: How about grammar? Like having verbs, nouns, adjectives?
L: OK, that's another feature. And it's a good example...
D: I mean I mention this cause like in my biology class last year, I kind of
remember talking about a study on prairie dogs, where, I think the researchers
claimed that the warning cries of prairie dogs constitute language, because
they have this, different parts of speech. You know, like nouns, to name the
type of predator they spotted, adjectives to describe its size and shape,
verbs..., but now it seems like...
L: All right, hold on a moment. I'm familiar with the study you're talking about.
And for those of you who don't know, prairie dogs are not actually dogs.
They're type of rodent who burrows in the ground and the grasslands of the
west United States and Mexico. And in this study, the researchers looked at
the high-pitched barks a prairie dog makes when it spots predator. And from
this they made some pretty.., well, they made some claims about these calls
qualifying as an actual language, with its own primitive grammar. But actually,
these warning calls are no different from those found among certain types of
monkeys. Well, let's not even get into the question whether concepts like noun
and verb can be meaningfully applied to animal communication. Another thing
that distinguishes a real language is a property we call "discreteness". In other
words, messages are built up out of smaller parts, sentences out of words,
words out of individual sounds, etc. Now maybe you could say that the prairie
dog's message is built from smaller parts, like say for example, our prairie
dogs spot a predator, a big coyote approaching rapidly. So the prairie dog
makes a call that means "coyote", then one that means "large", and then
another one to indicate its speed. But you really suppose it makes any
difference what order these calls come in? No. But the discrete units that make
up language can be put together in different ways. Those smaller parts can be
used to form an infinite number of messages, including messages that are
completely novel, that have never been expressed before. For example, we
can differentiate between: "A large coyote moves fast." and say "Move the
large coyote fast." or "Move fast, large coyote.", and I truly doubt whether
anyone has ever uttered either of these sentences before. Human language is
productive and open-ended communication system, whereas no other
communication system has this property. And another feature of language
that's not displayed by any form of animal communication is what we call
"displacement". That is, language is abstract enough that we can talk about
things that aren't present here and now. Things like "My friend Jo is not in the
room." or "It will probably rain next Thursday." Prairie dogs may be able to tell
you about a hawk at circling over head right now, but they never show any
inclination to describe the one they saw last week.
