P.Z. Myers and I first became acquainted with each other many years ago through a Usenet group called Talk.Origins. My wife suggested that a couple of those all-but-forgotten articles should be revived and posted on my blog. OK honey, whatever you say. One of the two I would like to show is from the 4th of July 2002 that was awarded Post-of-the-Month. Amusingly, my wife found out after reading the post that it had already been referenced just last year, right here on FtB, byStephen ” DarkSyde” Andrew of Zingularity, another Talk.Origins alumnus. His article looks pretty good and even has an updated follow-up. Here is the [edited/updated] original.
A few days ago, “Joe Cool”, [email address withheld] wrote the following;
>man, if you want to believe your great^100 grandpa was a rock, be my
>guest…but it’s STUPID!
Well yes, that would be pretty stupid. Clearly you don’t have an adequate grasp of either the actual concept of evolutionary ancestry or of the significant time factors involved. I think you need a whole lot more zeros as well as a more realistic ultimate original entity.
I figure at 20 years per generation, 100 generations of grandfathers would equate to twenty centuries. That means the grandpa you’re talking about was a contemporary of rabbi Yeshua bar Yosseff just 2,000 years ago. Not quite an adequate evolutionary time-scale and certainly far from the mark when talking about the origin of life on Earth. But even 100 years ago, 16 years per generation was more the norm, as it was with my grandparents and many of their ancestors. That would have put your great^100 grandpa in the time of another wildly exaggerated hero, King Arthur, the other “once and future king” in about the 5th century of the common era.
Increasing the multiple, your great^1,000 grandpa would have had even shorter generation gaps, being about 14 or 15 years apart on average. He would have been a Paleolithic nomad in about 13,000 BCE, just shortly before the foundation of the most ancient cities like Jericho and Damascus. He still would have been fully human and already a member of the only surviving human species, Homo sapiens.
Your great^10,000 grandpa would have been everyone else’s great grandpa too. (Everyone alive today that is) He would still have been definitely human and visibly different from his Neanderthal neighbors. Whether he would be considered Homo sapiens yet 140,000 years ago or still classified as Homo antecessor or heidelbergensis doesn’t really matter. All are still obviously people, albeit primitive.
Your great^100,000 grandpa might now be called Homo ergaster or erectus having lived some 1.3 million years ago. And his great^10,000 grandfathers would have been called Homo habilis or maybe rudolfensis. Any or all of them would have appeared to be a bit more ape-like than the most monkey-faced modern guy, but he still would have been definitely human, especially when compared to the other fully bipedal apes that were wandering around a million-and-a-half to a couple million years ago. If you were to put your erectine or habiline grandpa on a crowded pew in your church, he would have looked like an ape-man. But if you saw him amongst his natural neighbors, the paranthropines, you would have seen him as nothing less than a man. However, the generations would be shorter, now being something like 13 or 12 years apart on average.
At six or seven years between generations, your great^10 million grandpa would have been barely recognizable as a primate, looking almost as much like a squirrel-like sort of thing. He might have witnessed the demise of the dinosaurs, or he would have grown up in the harsh wasteland that was the wake of the KT impact for so many years. Now the generation gap really begins to close. For most of the Mesozoic era and a long time before that, the age difference between father and son would only be about a year.
Your great^100 million grandpa was a shrew-like mammal darting through the Jurassic underbrush 170 million years ago. The amniotic sacs his great^10,000 grandchildren were born in didn’t have quite the same integrity that his great^10,000 grandfather’s birth-sacs had. Although leathery and easily torn, they would still have been considered egg “shells” much like some snakes are born in today. This grandpa would have already been mammalian, but not yet placental.
Your great^1 billion grandpa would have lived under water along with everything else, including trilobites and some really alien beasties a few hundred million years ago, and at least a couple hundred million years before the first dinosaur. The generation gap is now a monthly rather than yearly division. But for most of the last half-billion years of our genealogy, that wasn’t the case. In 400 million years, your ancestors went from toothy swimming worms like conodonts and pikia and became crossopterygian fish and then tetrapoidal amphibians, synapsid “reptiles”, and even amniotic proto-mammalian cynodonts. But the generations before that were far less interesting.
The world of your great^10 billion grandfather wasn’t much different than that which was already described, although there were a lot fewer trilobites then. He wasn’t even a swimming worm yet. He would have been more like a roundworm, if he would have been considered a worm at all. He may have looked more like a jellyfish with a sense of direction. Before that, he may have been something even simpler, like a microbial sponge-nymph, but still definitely a metazoic animal, even if he wasn’t really a “he” in the sense of discernable gender anymore.
Your great^100 billion grand-whatever ancestor may not have even been an animal yet, but a kind of slime-mould, which is still a eukaryotic organism.
Your great^1 trillion ancestor would have been bacteria and your great^10 trillion ancestor would have been bacterial too, although we are no longer talking about anything recognizable as an exclusively evolutionary phylogeny. Instead your genealogy would be completely befuddled by an intractable mash-up of horizontal gene transfer and endosymbiosis, not really an ancestry at all.
Your great^100 trillion -um- predecessor may have been an even simpler replicative protein in an inhospitable world unrecognizable as Earth. Now we’re no longer talking about evolution or endosymbiosis, but abiogenesis, another wholly different string of processes. In any case, none of your lineage would ever have been rocks. Rocks tend not to reproduce for some reason and therefore cannot evolve.
I know elements of this tend to be confusing for a lot of people. A decade ago, some of it confused me too. So I intend to flesh out species-level classifications from a paleontological perspective in an up-coming lecture, either in Houston or at LSU, but neither date has yet been set.