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10/30/2001
Back to the Sea
Wall Street optimists are predicting and hoping for the market to
show a V-shaped recovery from the lows after September 11.
After a disastrous round of golf last week, I plotted my few golf
scores for the year - almost a perfect V-shaped pattern. I started
with a very very high score, dropped to just a very high score,
then a sharp rise back to my original starting point. Fine for the
Dow Jones but not for golf. Why this tendency to return from
whence I''ve come?
You might ask the same question in nature. Why would
evolution produce a monumental example of a return to whence
life originated - the sea? Last week, I mentioned a little creature
resembling a mouse that was the size of a paper clip. This little
guy with mammalian features was scampering around with the
dinosaurs nearly 200 million years ago. Both the dinosaurs and
the little guy''s ancestors had pulled themselves out of the ocean
or lakes or ponds or other aquatic environments and learned to
enjoy the benefits of living their lives on land.
When the dinosaurs got knocked off by that errant asteroid or
whatever, the little mammals blossomed and all kinds of strange
creatures came into being. I would say we humans are the
strangest. Other species that developed after the dinosaur
extinction were the ungulates - animals with hoofs. Those early
ungulates were nothing particularly spectacular, four-footed
animals with tails. Certainly not the type of animal that you
would think to evolve into the largest animal the earth has ever
seen.
You may be saying that the largest animal is obviously the whale
and that it''s not likely that a hoofed animal like a pig could be the
ancestor of the whale. Ok, maybe not a pig, but now we''re really
beginning to pin down the "back-to-the-sea" saga of one big
mammal. It has been known for a long time that the whale once
was a landlubber like ourselves. I looked up whales in my 1962
World Book Encyclopedia and found that the article was written
by famed explorer Roy Chapman Andrews. Andrews cited his
own personal experience with a humpback whale and evidence
that the whale once walked on land. Normally, the vestigial legs
in whales are small bones that are hidden inside the whale''s
body. In this particular case the whale''s "legs" extended nearly
two feet outside the body.
While the evidence pointed to whales having a previous life on
land, the details remained a mystery until the last 10-15 years.
The situation has changed dramatically with the finding of fossils
of the whale''s early ancestors. An article by Douglas Chadwick
titled "Evolution of Whales" in November National Geographic
tells the story of this recent work. You wouldn''t recognize the
first whale. It was a spinoff of the ungulate family that obviously
had an interest in water. To me, the artist''s conception of this
fellow, known as Pakicetus, looks sort of like a weasel with an
oversize head and webbed hind feet. It lived around 50 million
years ago with our own ancestors, who were then primates about
the size of a squirrel.
Paki, as I''ll call it, certainly doesn''t look like a whale but
scientists are calling it just that. The reason is that certain
features of its skull are common to what we recognize as real
whales but these features are not found in other mammals. In
1994, in Pakistan, they found a fossil of a more fearsome guy
about the size of a sea lion with four webbed feet. You know it
came from ungulate heritage from the fact there was a hoof on
the end of each toe. It walked and swam around about 49 million
years ago and had a mouth full of teeth that you would definitely
want to avoid.
Skip along a mere ten million years and there are no more
walking-swimming whales. The front legs have evolved into
flippers and the back legs have disappeared or also turned into
flippers. Also, unlike the early walking-swimming whale, the
later whale no longer had to drink fresh water but could manage
in the salty ocean. In this relatively brief time geologically
speaking, the whale has become a true marine animal with many
changes in shape, becoming more streamlined with a shorter
neck and loss of features such as hip bones. This allowed the
spinal column to become flexible enough to power the incoming
tail flukes to drive this big animal. Whales also lost their outer
ears, with the lower jawbone sending sounds to the inner ear.
Finally, jump forward to 15 million years ago and you have
dolphins in the picture.
Jump again to today and you have blue whales 110 feet in length
and weighing over 300,000 pounds. How do whales differ from
their fishy companions? Being mammals, whales give birth to
live offspring, while fish lay eggs. It''s a good thing that whales
live in water with its buoyancy. Otherwise, it would be a bit of a
pain to carry and give birth to a 25-foot, 8-ton baby!
Unlike fish, whales are warm blooded and keep their constant
body temperature by growing thick layers of blubber; the colder
the oceans, the thicker the blubber. There are now two general
types of whales, the baleen whales and the toothed whales. The
really big whales are baleen whales, which swim around with
their mouths open and then force the water out through comb-
like structures that strain out the small stuff like shrimp upon
which the whale dines. The smaller toothed whales live on
larger fish or other prey in the sea. Dolphins are in the toothed
whale category and the really large dolphins are the killer
whales.
The toothed whales, such as the modern dolphins, have also
come up with what''s known as a melon. This structure sits in the
top of this toothed whale''s head and sends out sounds. When the
sound hits an object, the echo comes back and is detected in the
dolphin''s lower jaw. Thus the dolphin joins bats and other
species in using a form of radar eons before man came up with
the idea.
So, what''s the future for whales. Could it be the hippopotamus?
DNA studies show that indeed the hippo is the closest cousin to
the whale among us landlubbers. Norihiro Okada in Japan has
found shared markers in the genes of whales and hippos that he
maintains shows that they share the same ungulate ancestor.
Another article in the same Geographic by Mark Deeble and
Victoria Stone on life in Kenya''s Mzima Springs deals primarily
with the life of hippos in that area. The hippos essentially spent
all day lazing around in the three pools of this protected area of
Kenya. They get to work feeding themselves at night by grazing
on grasslands. The hippo''s daytime experience is like going to a
fancy spa. The treatment isn''t quite the same as a visit to
Georgette Klinger but it''s close. If you think I''m kidding, look at
that contented hippo with its mouth wide open while the fish
clean it out. According to the article, the hippos are so relaxed
during this treatment that they sometimes fall asleep! (I assume
they wake up in time to put their heads out of water and take a
breath.) The hippos also encourage the fish to clean up wounds
and other parts of their bodies. With amenities like this, I
wouldn''t be at all surprised if eventually the hippos evolve into a
more streamlined animal that lives mostly in the water.
So, the next time you go to the zoo, you might want to take a
closer look at the hippos. They could be a work in progress.
Allen F. Bortrum
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