How many generations back does our lineage go?

by phil on Wednesday Aug 22, 2007 11:13 PM
evolution as a way to appreciate life, evolution_old

We have at least 300 million generations behind us.

Dawkins estimates, very roughly, that some kind of worm is our concestor ("common ancestor") 590 million years ago. He estimates that it is our 300-million-greats-grandparent. Pondering the implications of that is astounding. That means that at least 300 million animals survived to an old enough age to reproduce, and did. My DNA contains the remnants of at least 300 million consecutive success stories in surviving and reproducing. This makes it no surprise that we are so hungry to mate and reproduce. It also makes suicide and homosexuality interesting puzzles.

And bizzarely enough, I think about this. Do I want to be the end point of that 300 million long chain? Do I want to be the first one in my line to drop the baton?

We don't know exactly what worm it is, but it is some kind of worm. That is only to say that is a long thing, bilaterally symmetrical, with a left and a right side, a dorsal and a ventral side, and a head and a tail end. 590 million years later, and we humans still follow that basic template.

I culled this information from The Ancestor's Tale by Richard Dawkins.

This book is going in my Hall of Fame. It's modeled after Chaucer's The Canterbury Tales. It's segmented into 40 rendezvous with various concestors starting with Humankind's "Eve," then continuing to Chimpanzees and so on all the way back to Eubacteria. They're rendezvous points because we re-unite with our long-lost relatives when we discover our concestors.

This book is exactly the kind of book I fantasized about writing when I imagined my writing and recollection skills of grand caliber. Here's an excerpt:

Any animal that moves, in the sense of covering the ground from A to B rather than just sitting in one place and waving its arms or pumping water through itself, is likely to need a specialised front end. It might as well have a name, so let's call it the head. The head hits novelty first. It makes sense to take in food at the end that encounters it first, and to concentrate the sense organs there too — eyes perhaps, some kind of feelers, organs of taste and smell. Then the main concentration of nervous tissue — the brain — had best be near the sense organs, and near the sense organs, and near the action at the front end, where the food-catching apparatus is. So we can define the head end as the leading end, the one with the mouth, the main sense organs and the brain, if there is one. Another good idea is to void wastes somewhere near the back end, far from the mouth, to avoid re-imbibing what has just been passed out. (p. 386)

Dawkins "gets it."