Tuesday, May 07, 2013

Remembering uncle Sah

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.

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