In the beginning
My uncle was different from
the others although I was never able to put my finger on it exactly.
Sure, he was smarter than most and in some ways he didn't look like
everyone else I suppose. Now his eyes, the way he looked at you, as
though he knew something you didn't. It was a little spooky at times,
but I knew my uncle liked me a lot.
Memories however grow dim,
especially after some 7 million years. My uncle's full name is
Sahelanthropus (sa-ha-lan-throw-pus) Tchadensis (cha-den-sis), but
I've always called him Sah. Scientists, at least for the present,
believe he's the best candidate for our last common ancestor with the
chimpanzee.
Sah lived in Chad, Africa.
Seven million years ago, give or take, was when we diverged from the
chimp. We went our separate ways. This is difficult for a lot of
humans to accept, how we're all related to Uncle Sah that is.
The big family
“Family is everything,”
many of us like to glibly proclaim but it seems more like lip service
than anything else, at least a lot of the time. We know now that all
life shares a common ancestor, where our DNA ultimately came from.
Our family literally includes the humpback whale, the bald eagle and
the fruit fly. It's loud, boisterous, sometime bizarre and certainly
diverse. Yes, family is everything.
The Human Genome Project was
completed in 2003. We identified the approximately 20,000-25,000
genes in human DNA, the instruction manual for making a human. We
also determined the sequence of the 3 billion chemical base pairs
that make up human DNA. We have enough data now to study and analyze
for the next 100 years. DNA in living cells, to the best of our
knowledge, is universal and combined with the theory of evolution is
a model of how life is, came to be and its origins.
Knowing what we know
Geneticists speak about
“pseudo genes,” genes that once functioned in our ancestors but
are no longer functioning. But of course, we haven't always been
human. It appears in fact that we have not evolved that much because
our evolution has been more about loss of gene function.
This is where environment
has a great deal to do with who we are today. A million years ago one
of our ancestors “discovered” fire and some 10,000 years ago
began the Neolithic Age and the development of agriculture. Diets
changed, food was cooked, cooperation and communication on a large scale became
necessary and we consumed more starches.
Over a relatively long
period of time we found we no longer needed such strong jaw muscles,
which required a bony head that limited brain development. Our heads
gradually became round, which helped increase brain size.
Both chimps and humans have
the amylase gene for digesting starch but chimpanzees have two of
these genes and humans have six. As farming culture developed this
particular gene became more important. Interestingly, human
populations that do not farm, such as the Australian aborigines, have
fewer amylase genes.
Some 75 percent of our
identified disease causing genes, such as Huntington, Parkinson and
some types of cancers have been identified in fruit flies. As well,
what is called the pax6 gene regulates eye development in flies, mice
and ourselves. The fruit fly has turned out to be extremely important
in analyzing certain conditions found in humans. Fruit flies respond
like humans to alcohol consumption, from hyperactivity to passing
out. They're used in studying insomnia and severe aggression, and
altered serotonin levels in flies have resulted in a male-male sexual
orientation in the mutants.
The Neanderthal, who died
out some 25,000 years ago, is probably the last divergent branch of
our evolutionary tree. Approximately 2.5 percent of our DNA outside
of Africa comes from the Neanderthal. We likely met up somewhere in
the Middle East for a brief encounter.
The FOXP2 gene, which is
called the language gene, is identical in both humans and
Neanderthal. It appears however that certain genes in cognitive
development are different between humans and Neanderthal, possibly
because Neanderthals and humans had to solve different types of
problems, like anticipating prey for example or simply “life
styles.”
The short and long of it
All life on this planet is
intimately related. It goes way beyond “loving thy neighbor.” The
“them” is us. Homo sapians, collectively, are not an especially
lovable species and one could argue that the planet would be better
served if we simply went away.
On the other hand, an
evolutionary breakthrough could occur, a gene switched on or off and
our behavior changed or modified. The extraordinary achievement of
mapping the human genome (as well as other species) has the potential
for amazing possibilities, both good … and bad. A good first step
is understanding how large our real family is and our responsibility
in protecting it. That may be the best hope for our survival.
