DNA testing

So apparently if you get one of those DNA tests, they send you a chart that shows you all the percentages of what ethnicities you are. Then you get to pick out the one that is coolest and be that, as if only that little slice of your genetic heritage made you what you are. But sadly, your Cherokee great great great grandmother didn’t leave you the least bit Cherokee other than a smidgen of Cherokee genes, or your Zulu great great grandfather or the one Irish great grandmother left you neither Zulu nor Irish. Think about it like math–an eighth (your great grandparent) or a sixteenth (your great grandparent) or a 32nd (your great great great grandparent) is just a tiny little bit of you, and the other seven eighths and fifteen sixteenths and 31/32nds long ago washed out most of that inheritance. You are what you are, which is whatever most of you is, all mixed up together, blended, and poured anew into what became you after hopefully a terrific simultaneous orgasm. Your Cherokee great great great grandmother would never even recognize you as one of her own, nor would you take in anyone who said he has 1/32nd of your own genetic background. After all, there are probably hundreds just like him out there, all equally related to that same woman who was born maybe two centuries ago. Which kind of takes the shine off of those DNA tests. It’s just DNA. But it doesn’t mean you have any actually viable connection to any of your distant ancestors other than sharing some of the same genes. And many (if not most or all) of those genes would have mutated during some of those successful couplings between you and your great great great grandmother anyway, so they aren’t even all the same genes. Go back far enough, in fact, and provided you do not come from a carefully maintained line of strict inbreeding (sisters marrying brothers) there will likely not be a single genetic behavioral trait–that is, something that makes your personality distinctly you–remaining that you share directly from your very distant ancestor. The genes behind those traits have all been replaced during successful couplings since then. The raw material of genetics are there, and have always been there, since life began, but the actual genes last only so long. None of us share any of the exact same genes from critters millions of years ago that we have descended from (the synapsids, or mammal like reptiles, for instance), and none of us are passing on specific genetic traits from even several hundred years ago. Maybe your great great great grandfather from Ireland was a writer. And maybe you’re a writer. Did you inherit writing from him? Nope. Lots of people are writers. It just so happens that two people out of the 32 people in the line from your great great great grandparent to you happen to be writers. And two out of thirty-two is almost surely nothing more than coincidence. You might look like him…but then you might look like people you are not directly descended from. After all, that great great great grandfather is only one out of 32 grandparents having sex 16 specific times that gives you the DNA that, all mixed together and randomly mutated, is you. You are much more likely a writer because you had a good English teacher than because one of those 32 great great great grandparents also wrote. Culture trumps genetics in most human endeavors.

Stick with reincarnation. That gets around the whole genetics thing, saves you money on DNA testing, and maybe you slept with Shirley MacLaine in Ancient Egypt. She was a queen. You a slave boy with gumption. Torrid passions two hundred generations ago in the shadows of the pyramids. I mean why not? Though that might make you 1/1280 of yourself in a past life.

Mammal-Like Reptiles

None of my Synapsid ancestors were writers.

 

Advertisements

Monotremes and you and me

Found this buried in among the drafts and I have no idea when it was…

It began as a post about a donkey in a hole. Farmer shovels in dirt, donkey takes a step up, farmer shovels in more dirt, donkey takes another step up. Finally the donkey is out of the hole and the hole isn’t even a hole, it’s full of dirt. The lady had thought maybe it was a real story–the picture of the donkey in the hole–and hated the farmer. Not sure why, but on Facebook you have to hate something. Me, I hate cat pictures. This lady hates farmers with donkeys in holes. I stopped paying attention. A day or two later I check in again, unintentionally. The thread had gone off topic, from donkeys to platypuses. Placental mammals to monotremes. The lady hated platypuses. Why do you hate platypuses, someone asked. They lay eggs, she said. Another guy said it’s because they’re monotremes, sort of a link between mammals and reptiles. The lady said eww….

Eww? Have you ever seen a platypus or an echidna, I asked. I mean, they’re adorable. Personally I love echidnas. I’ve never seen a real platypus…there aren’t any outside Australia, not even in zoos.  They have laws keeping them there. Echidnas, though, are in zoos all over the place. Some come from Australia, some from New Guinea, they look kinda like hedgehogs and trundle about looking for ants mostly and are cute as hell. The L.A. Zoo had a whole indoor display full of eucalyptus and koalas and echidnas. The koalas mostly slept, the echidnas trundled. I was being kind of Facebook obnoxious, I have to admit. But I was only beginning.

Because to be one of those really obnoxious Facebook people, I explained that a monotreme is actually a living example of one of the earliest stages of mammalian evolution, an early stage on the track which went from which from monotremes like echidnas and platypuses to marsupials like kangaroos and wallabies to placental mammals like you and me. And to be even more incredibly obnoxious, I explained that mammals didn’t evolve out of reptiles, synapsids did. The early synapsids are called  pelycosaurs, the most famous of which is the sail-backed dimetrodon.

Dimetrodon, about 275 million years ago.

Every child’s  favorite pelycosaur, the Dimetrodon, about 275 million years ago.

Most synapsids were much less exotic looking, however. And one, sans sail, evolved into therapsids, aka the mammal-like reptiles, from whence we eventually came.

The weirdly cat-like Pristerognathus, about 260 million years ago.

The weirdly cat-like therapsid Pristerognathus, about 260 million years ago.

Alas, nearly all the pelycosaurs and therapsids died out in the Permian extinction event (which took out 90% of all know species on earth, actually). Just before that, though, in the late Permian, a line of therapsids had evolved into the way more mammal like cynodonts, some of which somehow survived the Permian extinction to continue in the Triassic, a world virtually bare of species and ripe for dramatic evolutionary change, especially among reptiles. Hence all those wacky dinosaurs. Cynodonts, in comparison, seem much more mundane and functional. No cynodonts became tyrannosaurs or apatosauruses. None ever rose out of our imaginations to level Tokyo.

But one line of cynodonts that had survived the extinction eventually evolved into early mammals sometime in the latter half of the Jurassic, little shrew looking things that hid in the shadows from dinosaurs and were predecessors of the echidna and platypus and in the long run, you and me. But it would take another extinction event, this time a massive meteorite or comet, to end reptile dominance and enable our skulking little shrew-like predecessors to evolve into a zillion species and fill niches world wide. Actually not all were shrewlike, some may even have been downright cute, for egg layers:

At eighteen inches long, castorocauda was more like a platypus than a shrew, 160 million years ago.

160 million years ago the castorocauda, at eighteen inches long, looking more like a platypus than a shrew

However, you and me, being primates, probably did evolve out of the sneaky little shrew like creatures skulking about in the dark. But we didn’t evolve directly out of reptiles. And we are not related to dinosaurs at all. What did evolve directly out of reptiles, of course, were birds, which actually are dinosaurs, the only surviving dinosaurs who then radiated globally into a zillion species in the global emptiness follow mass extinction. And just as chickens are dinosaurs, we humans all still synapsids, like the dimetrodon. In fact, synapsids are much older than dinosaurs, which means that birds are actually a later creation than are mammals. Way later. Hence we keep them in cages and dice them into McNuggets. And when you look at a raven and think that’s a dinosaur? It could be looking at you and thinking and that’s a synapsid? Except all it’s really thinking is that it wants your sandwich.

What does this have to do with a donkey in a hole, someone said.