Human family tree is a tangled, messy bush
- From: "simple_language@xxxxxxxxx" <simple_language@xxxxxxxxx>
- Date: Fri, 31 Aug 2007 07:08:40 -0700
source: http://www.livescience.com/history/070831_hn_family_tree.html
For anthropology students 30 years ago, learning human evolution was a
breeze. It went from Australopithecus to Homo habilis to Homo erectus
to various Homo sapiens. It was a straight shot that one could learn
in a few minutes late at night while cramming for an exam.
But in the late 1970s, we entered a golden age of human fossil
discoveries that has repeatedly punched holes in the naive idea that
our evolution would be that clear, clean, and straight.
Like most animals, humans have a checked past, and our family album is
now full of side branches and dead ends. And it's populated with
creatures, such as the little people (Homo floresiensis) of Flores
Island in Indonesia, that we could never have imagined in our wildest
dreams.
The straight line has blossomed into a spreading, rather uncontrolled
bush and we don't like it. We want our history to be nice and neat,
but the fossils keep messing us up.
This summer, scientists announced the discovery of two human fossils
found in Kenya in 2000. One is a 1.44 million-year-old Homo habilis,
the first member of our genus, and the other is a 1.55 million-year-
old Homo erectus, a larger brained, much more sophisticated kind of
human.
Although paleoanthropologsts have assumed that habilis evolved into
erectus, it looks like these creatures spent time together on the
shores of Lake Tanganika.
The big news, then, is that these very different fossils are being
hung on the human family tree on separate branches but at the same
height. And once again, we have to reconsider the path of human
evolution.
But should we be all that surprised?
We want the first bipedal humans to stay out of the trees, but their
curved hand bones suggest they spent time swinging in the canopy like
apes; we want brain size to increase in lock step with tool use, but
tools appear before big brains; we want an orderly diaspora out of
Africa and across the globe by culturally armed early humans, but it
looks like people kept leaving all the time in fits and starts that
don't correlate with anything; and we want the last 200,000 years of
human evolution, the time when modern Homo sapiens appeared, to make
some kind of sense, but it doesn't.
.
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