When you've cleared that nasty little image from your mind, turn your attention to this: why aren't you a Neanderthal? That is, why is that Neanderthals, which dominated Europe for half a million years, lost out to old H. sapiens sapiens?
There have been dozens of theories, but I'm not here to debunk those golden oldies. In fact, I'm going to ignore most mainstream theory. Do I not have my own degrees in geology and biology? Yes! Have I not spent many summers doing paleontological excavations? I have! And where all those digs for dinosaurs and fossil fish that have nothing to do with human ancestors? Hell yes, but that doesn't stop me from having my own crazy theory.
I think we were sexier than them.
Neanderthals and modern humans are pretty closely related. At times over the last century, scientists have even classified Neanderthals as a subspecies of Homo sapiens. These days the first Europeans are settled in more definitively as a species of their own (H. neanderthalensis). Despite what Jack Chick and the fine folks of Chick Publications put out in their hilarious little tracts, Neanderthals are known from literally thousands of specimens found across Europe and the Middle East.
Despite their close relationship, if you were to pass a Neanderthal on the street, you'd have a pretty good idea that you'd seen something strange. Neanderthals were overall bigger than us. Not necessarily taller (though they were not the squat, slump-shouldered brutes of the movies), but bigger boned and more heavily muscled. If you've ever looked at the incredibly massive muscles on a gorilla, you'll have some sense of what it would be like to see a Neanderthal's biceps. Which isn't to say they looked like apes. Neanderthals were definitely people. There were a laundry list of different features in their skulls: a heavy brow ridge, a low, flat elongated shape that would been the envy of any Mayan, and a knot of bone at the back of the head that would have looked something like a hair-bun. Oh, and their brains were slightly bigger than ours. Neanderthals also had a somewhat pushed out mid-face and a weak to nonexistent chin. They had big noses, barrel chests, and bowed legs. You may think your building super looks like a Neanderthal, but chances are the real thing was even uglier. Probably.
And yet the question remains, why didn't we have nookie with these guys?
Face it, people will shag anything. If you think ugly is protection against reproduction, you haven't been looking closely enough at the clientele at your local Wal-Mart. Especially the folks that wander in after midnight. Ugly reproduces just fine, thanks.
It's not like we didn't have a chance to meet. Modern humans and Neanderthals interacted in Europe for millennia. Maybe that period was several thousand years of warfare. Heck, maybe we made Neanderthal stew. But there was enough cross-pollination of culture that after the moderns moved in, Neanderthals began to spice up their tool kit (which had been unchanged for a long, long time) with new items very similar to those us H. sapiens types were carrying. In the Middle East, Neanderthals and modern humans lived practically next door to each other. Close enough to wander over to a jar of mammoth fat.
Yet studies have found almost no evidence that we cross bred with these guys. Sure, there have been a few specimens, like the child from Mezmaikaya Cave, that have features of both species, but such events appear to have been very rare, if they happened at all.
So how come?
The Chimpanzee Dilemma
To find out why ancient man was not tempted by Neanderthal sugar (why why ancient woman didn't fall for these proto-football players), we can look at our surviving relatives. Yes, chimpanzees, bonobos, and gorillas are a lot more distantly related to us than Neanderthals. Neanderthals and modern man probably share a common ancestor no more than a million years back. Us and our ape kin branched off somewhere around six times as long ago. Still, we're pretty darn close genetically to the other great apes (hey, did you know you were a Great Ape?) and I suspect that there's some sneaky clues about our own past living right here and now.
The Common Chimpanzee (Pan trogolodytes) is an extremely interesting critter. Not only is they genetically similar to humans, chimps share our fondness for social groups, tools (including inventive uses for leaves, sticks, and stones), for smacking around other chimps of lesser status, and murder. What they do not share are our sexual habits.
Unlike humans, who copulate at the drop of a hat (and who keep plenty of hats on hand to drop), chimps only mate during the female's estrus, which is signalled by blood engorging the female's posterior. In other words, when a female chimp is fertile, she signals this by a huge wrinkled red swollen thing that extends off her ass. The sight of this red shiny mass triggers a switch inside the male chimp's brain. The chimp which has done the best job of slapping other male chimps into submission runs over, jumps the female chimp, and five seconds later, it's over. When it's not reproductive time, that big red balloon deflates and disappears, and males go back to the all important smacking.
Chimps do not seem to engage in sex for fun. That alone shows that, relatives they may be, they are not people.
Only when reproduction is successful does the female chip develop noticeable breasts. These seem to act as an actual deterrent to males, decreasing their interest in keeping this female around. Chimps usually give birth to single infants and, like humans, have a lot to teach the little one before it can join in the clan. So mom will first nurse and then care for her kid for a period of five to seven years. During this time, she generally has no sex at all. It's a good thing chimp sex seems to be so unsatisfying. Otherwise, they might explode from frustration.
One big result of the chimpanzee breeding strategy is a very low reproductive rate. Chimps live about as long as humans do (to sixty years or more), and females are fertile from about age ten to as late as forty. But it's a rare female chimp that manages to get more than a couple of kids born, raised, and delivered alive to add to the gene pool. As a result, it takes almost ideal conditions for chimp populations just to hold their own. Stress them, and they vanish. Fast.
Here's the quick summary of chimp reproduction: swollen rear, good. Breasts or kids, bad. Reproduction at long intervals. No sex for fun.
Here's one other interesting sexual tidbit about our Chimpanzee relatives: males have small...equipment. Even accounting for their difference in body size, they're significantly smaller than that of humans (though twice as big as the one-inchers most gorillas are packing). So the next time you're feeling inadequate, don't buy yourself a Hummer. Just visit the zoo and lord your manly appendage over our pitifully endowed ape brothers.
The Crazy Theory
What does the sex life of chimps have to do with the extinction of the Neanderthals? Maybe everything.
Neanderthals are people, so it's easy to think of them as being pretty well like us. Big boned, big nosed, ugly versions of us. But the fossil record is very poor at preserving soft tissue. Tissue like breasts. Tissue like a penis.
So here's the theory: humans and Neanderthals did not interbreed because the two species had different reproductive strategies. Neanderthals, living in a tough environment and small groups, may not have engaged in sex for pleasure. More than that, they may not have had any of the secondary sexual characteristics that attract human males (read this as Neanderthal chicks were not only ugly, they had no tatas). Bundled in clothing, humans might have even had trouble telling Neanderthal males from the females.
It's even quite possible that humans and Neaderthals just were not sexually equipped to service each other. Our sexual gear is bigger than any other primate's by a factor of two. A human penis might have been too large for a Neanderthal female. A Neanderthal penis might have looked tiny to a human female (that is, if they could stomach our females with those repulsive things on their chests).
Despite living side by side, despite both being smart, social, tool-making beings, humans and Neaderthals were just sexually incompatible and so did not cross breed.
Evidence? What do you mean evidence?
The best crazy theories are those that sound good on paper, but have no real evidence to back them up. I'm about to break the mad scientist's code, because I'm going to give you three bits of data I think support my theory.
- Bonobos. The Common Chimpanzee isn't the only kind of chimp around. There are actually at least two species (and some studies suggest three or more). One of these species is Pan paniscus, otherwise known as the Bonobo. Bonobos are smaller than P. trogolodytes, which is why they've sometimes been called "Pygmy Chimpanzees." Another big difference between the two: Bonobos love sex. Bonobos have sex all the time. Bonobos have sex to say hello, sex to say "what's for supper?," and more sex to say "wow, that was good sex." Bonobos don't need no damn hat. The fact that Bonobos and chimps, while being so closely related, have such different sexual habits shows that it's perfectly possible for two closely related primates to have very different sets of sexual behavior.
- No Chimpmen. Okay, avert your eyes if you can't take an icky suggestion. I know you've got a pretty good constitution to make it this far. Avert anyway. Still looking? Okay, you asked for it. Depending on whose numbers you trust, humans and chimps share between 95% and 98% of their DNA. This is at least as close as the relationship between donkeys and horses. Donkeys and horses can cross-bred to produce infertile mules (and hinnies). So why are there no chimp-human hybrids trotting around? I mean, we're talking about a species (and here I mean humans) that will mount a goat when it's randy (we should be grateful that goats are much more distantly related). A couple of good reasons for this: chimps aren't interested, chimps don't carry the secondary characteristics that would sound men's buzzers, and (perhaps most importantly) a female chimp would likely rip your arms off and beat you over the head with them if you tried. Neanderthal females would have been homely, disinterested, and strong. That's a hard trio to overcome.
- The pelvic evidence. Actually, this isn't so much evidence as a solicitation for evidence. When women give birth, it tends to leave marks on their pelvic bones that are often valuable forensic signs of parentage. In other words, by looking at the bones, it's sometimes possible to estimate how many children a woman has had. So here's my pitch: someone with access to Neanderthal remains, take a look and see how many children Neanderthal females were cranking out. If they followed the "churn out a herd and let nature sort it out" method, their strategy might have been quite like that of modern humans. If it was the "two in a decade" result, they were likely following something closer to the Chimpanzee route.
Myself, I'm just going to set back and wait for that call from Sweden.