Evolution News: Sexual Selection Is A Major Element In Natural Selection

Elaine Meinel Supkis

I have gotten into increasingly frustrating debates with more than one theorist concerning human evolutionary forces. There is a fad these days to assume we evolved into what we are today due to the weather or volcanoes or hunting methods. It seems that people are forgetting the greatest force pushing evolution: sex. From day one when organisms evolved into two sexes, this is the main driving wheel of evolution. For many reasons, Homo Sapiens decided to use many visual clues for mating purposes.

By Sharon Parmet
Medical Center Public Affairs

In the Oct. 29 issue of Science, Bruce Lahn, Assistant Professor in Human Genetics and an expert on the evolution of the sex chromosomes, and his colleague, David Page, of the Whitehead Institute report that the X and Y chromosomes diverged from each other over the course of about 300 million years by going through four discrete stages rather than one smooth transition.

“By fossil digging on the sex chromosomes, we were able to reconstruct the four events that drove sex chromosomes into their distinctive X and Y forms and to date when these events occurred during evolution,” said Lahn. “The farther back in time we look, the more similar X and Y appear, boosting the theory that they arose from a pair of identical autosomes (nonsex-determining chromosomes),” he added.

Sex was not always determined by DNA. In many reptiles, the temperature at which the eggs are incubated determines the sex of the offspring. But when warm-blooded mammals with internal reproduction arose, sex determination by temperature became problematic. Shortly after mammals branched off from reptiles, approximately 300 million years ago, a regular pair of autosomes began evolving into what would become the modern X and Y chromosomes.

Many genes on the human Y chromosome have homologues (analogous genes) on the X chromosome. The presence of these X-Y genes reinforces the idea that the Y chromosome developed from an X-like ancestor.

To Lahn and Page, these X-Y genes serve as the “fossils” they can use to help reconstruct the evolutionary history of sex chromosomes. By comparing the number of mutations between the X form and the Y form of a pair of X-Y genes, Lahn and Page came up with rough estimates of when they were last alike, giving them a ‘geologic’ snapshot of sex chromosomes.

“The reconstruction of the defining events of human sex-chromosome evolution is analogous to the reconstruction of the evolution of species, except that we are looking at changes of a pair of chromosomes over geologic time rather than changes of whole organisms,” said Lahn.

When things try to stay alive, they are subjected to all sorts of selective forces such as disease or even small changes in the environment which brutally eliminates various living organisms. Eating and avoiding being eaten contributes to evolution in a powerful way but the most powerful engine of change is sex or manipulating the sex lives of others. When living things seperated from each other and one became the egg maker and the other the sperm producer, natural selection caused the egg's investment in the future to increase rapidly while the sperm's investment remained much smaller, almost microscopic.

The ideal world for any sperm is to impregnate all eggs, everywhere, continuously. Eggs, on the other hand, can't afford to waste time mating with weak or undesirable sperm so the battle of the sexes has been the flywheel moving organisms into a wild variety. For the female wants excellence. She has to take a huge hit when she gambles on mating. She loses part of her own body in a significant way, she endangers herself by producing spawn and she has severe limits on reproduction so females who take care in impregnations tend to dominate most species.

Here is an example of a swan picking a fake swan as a mate because the fake has all the best attributes:

BERLIN (Reuters) - A swan has fallen in love with a plastic swan-shaped paddle boat on a pond in the German town of Muenster and has spent the past three weeks flirting with the vessel five times its size, a sailing instructor said Friday.

Peter Overschmidt, who operates a sailing school and rents the two-seat paddle boat on the Aasee pond, said the black swan with a bright red beak has not left the white swan boat's side since it flew in one day in early May.

"It seems like he's fallen in love," said Overschmidt. "He protects it, sits next to it all the time and chases away any sail boats that get anywhere nearby. He thinks the boat is a strong and attractive swan."

I have watched the mating dance in nature many times. A typical example in the avian universe is how turkeys mate. Unlike song birds, for example, turkey toms have nothing to do with the hens once the eggs are laid. But this doesn't mean the hens have no say in choosing mates! Once, my son and I came across over 50 wild turkeys in an open field. The hens were walking around the perimeter and in the center strutted over a dozen big toms. The toms were challenging each other. They have the ability to pump air into their chests forming a loud drum and when they gobble, the drum resonates. They puff up the feathers to look as big as possible and stretch the wings stiffly to the ground and then stamp their feet like flamenco dancers.

Then they rush at each other. It is a splendid, hard fight and the loser flattens his feathers and runs to the outer edges of the circle. The hens watch this with an eagle eye, keeping one eye open for any eagles above, and they rush over to the toms that win the fights and crouch on the ground making cooing sounds, heads weaving side to side. Then the victor gets to mount. The hens think, "What a HUNK!" and are deliriously happy to gain the attention of the winner.

I have watched deer mate, too. Once, I was going into the forest to cut firewood when two bucks came slamming through the trees. One wheeled around and charged into the other and they locked horns and shoved back and forth, snorting. A doe was right behind them, watching with such avid interest, she nearly bumped into me. All three broke up the struggle, flipped their tails and took off like lightning.

In most animal or bird populations, the females are the choosers. They want mates who are smart, of good size or strength or have attributes the female thinks are good things to have. I have watched bucks approach does in heat. The buck arches his neck and shakes his antler array to show strength and size and if the female is impressed, she flicks her tail sideways. The buck literally stomps up to her in order to show he is super heavy, not a whimp. It is rather funny to watch.

Same with horses. A stallion will fight other stallions but if the mare doesn't like him, she will tuck her tail firmly between her legs and you can't budge it at all. She will kick the stallion off and whirl around and nip at him with her teeth. It is rather a sport watching a stallion court a mare. She will play coy and move off, he trails after her, nuzzling her and nudging her. She might toss her mane and run a bit to see if he is good at running. She will put him through his paces quite smartly.

Once, at a horse show, a mare went into heat. A man I knew riding a stallion was downwind. They were doing dressage. Well, dressage is supposed to be proud stallions showing off. Well, the stallion dearly wanted to show the Welsh mare his sexual prowess. So he arched his neck as far as he could and began stamping his feet as hard as possible. Stomp stomp stomp. Then he reared up. Look at my *ahem* big ejection system! He danced around on his hind legs, very proud of himself. The rider was increasingly terrorized by this. The stallion began to think, "I will show her how I can fight predators by throwing off this creature who dares to sit on me!"

I ran to the lady holding the mare's lead line and told her to move downwind, fast. We all had a laugh about it afterwards.

Race horses can't be bred easily because the mare looks at the stallions and thinks, "What a scrawny neck! His hooves are too small! He doesn't stamp his hooves when he walks! Yuck!" What breeders do is tie up the poor mare, this is rape, you know, and then bring out some handsome, Ice Age hunk of a breed like Haflingers such as my Sparky, thick necked horses from mountains or far north, with big hooves and the mare will neigh and react with delight and flick her tail. Then the hunky stallion is removed and a race horse stallion is brought out after the mare is blindfolded. The Thoroughbred mounts the mare without any "by your leave" and then is removed before she figures out, she was cheated.

This brings me to the core problem of trying to pinpoint various "causes" for evolution. There is no simple cause and effect, it is various and there is no magic point in time that is distinctive. With humans, this is very much so. Namely, we have not only the classic Darwinian forces at work, we have one thing more: deliberate cultural choices which we impose on nature.

Here is a typical example from the Bradshaw Foundation:

The last glacial period was preceded by 1000 years of the coldest temperatures of the Late Pleistocene, apparently caused by the eruption of the Mount Toba volcano. The six year long volcanic winter and 1000-year-long instant Ice Age that followed Mount Toba's eruption may have decimated Modern Man's entire population. Genetic evidence suggests that Human population size fell to about 10,000 adults between 50 and 100 thousand years ago. The survivors from this global catastrophy would have found refuge in isolated tropical pockets, mainly in Equatorial Africa. Populations living in Europe and northern China would have been completely eliminated by the reduction of the summer temperatures by as much as 12 degrees centigrade.

Volcanic winter and instant Ice Age may help resolve the central but unstated paradox of the recent African origin of Humankind: if we are all so recently "Out of Africa", why do we not all look more African?

Because the volcanic winter and instant Ice Age would have reduced populations levels low enough for founder effects, genetic drift and local adaptations to produce rapid changes in the surviving populations, causing the peoples of the world to look so different today. In other words, Toba may have caused Modern Races to differentiate abruptly only 70,000 years ago, rather than gradually over one million years.

All trees flower, most humans are unaware of this only because most of them have tiny, greenish flowers. Trees will scatter pollen (male sex) all over kingdom come causing humans to sneeze and their eyes to water. Some of this pollen eventually bumps into the ovas which produce the seeds for future plants. Some trees propagate through roots as well as flowers. But insects began to "breed" tree flowers so they could use them for food. Various insects had different ideas as to what is attractive. Whenever they spotted an interesting mutation, they would spread that mutation's genes throughout the tree population.

Animals eating fruits and nuts of trees did the same thing. Trees that shared tasty morsels surrounding the seed were carried further away and disseminated far afield even though the effort to create a fruit is huge.

The animal/insect/bird esthetics drives evolution at a very hot clip. Humans have exploited this by controlling who has sex with whom with a vengence. We manipulate nature into producing a tremendous variety of tastes, colors, sizes and shapes from small genetic pools. We exploit every possible deformity and genetic flaw to create new types of plants and animals.

We do this to ourselves. Waves of humanoids would start in Africa, our continous cradle, and ripple rapidly outwards. Each wave would go as far as possible and then even come washing back into Africa again.

During our last 250,000 years of evolution, the earth's climate suddenly went into this yo-yo cycle of warm/cold vacillations which stressed all simian populations. During this, humanoids were in a pitched battle with each other over who gets to control the neighborhood and thanks to the forces of evolution coupled with some very violent activities, the winners of this struggle were homo sapiens. Homo sapien females, unlike any of the other great ape family groups, discovered a means of controlling natural selection so they could have mates with big brains who could understand how to protect and feed the family females and their babies. Universally, ape females force their infants to cling to their hair and ride on the mother's back.

Human mothers can't do this. Indeed, I would suggest, when looking for mates, human mothers looked to see if the males had scant hair on their bodies. This would mean they couldn't force the baby to fend for itself. Mothers that rejected their babies when helpless were mothers who didn't have the brains to figure out, helpless babies=smart adults. Smart mothers figured out schemes for carrying the smart babies. Stupid mothers would force the babies to cling to something. So a hairy father meant he probably had a hairy mother which meant she didn't probably have to care so closely, carrying the baby around which meant she probably wasn't sufficiently clever to make tools for carrying the baby.

In virtually all stone age cultures, the men use various schemes for attracting the eyes of the females. They wear various things, they groom themselves in distinctive ways, they dance around with farming and hunting tools, jumping in the air, shouting. Being able to draw pictures and tell stories or memorize the star positions and tell when seasons come and go, the ability to negotiate with strangers, all this was very important to women in the past and they willingly bore the young and carefully raised them if they were impressed with their mates. Various cultures have sprung up that tear at this system, namely, trying to force women into servitude. But this doesn't work unless the males provide the women with the things they need to raise babies.

The cultures that figured out how to manipulate their breeding so they produced vibrant communities flourished. The ones that didn't figure out how to do this, were driven into increasingly marginal lands. Human females have a sharp eye for appearances. We have ears sharply attuned to voice pitch, we have to puzzle out hidden meanings, the music of language is one of many tools we use to determine if someone is a cannibal who will eat our babies or a real potential father who will die for our babies. Psychopaths evolved because the genes of humans that can fool others always lurks in any population.

When humans left Africa and spread out across the planet, killing or driving out all other near or even distant relatives, the populations immediately differentiated, visually as well as linguistically. Each group had its own notions as to what was speech, what was beautiful or desirable. Eye shape, length of neck, legs, ears, nose or color of skin, color of hair, hair shape or style, eye color, any part of the body that could be seen with the eye or smelled with the nose was a candidate for special selections causing populations to be come very rapidly, variable.

A simple matter of where fat is deposited on the body has been used for mating choices. I sat in a parkinglot today, watching the tremendous variety of humans walking past. Short legs and big belly, tall and thin, pettite and small boned, fat only on the rump, fat mostly on the torso, some of the earliest representations of humans that look like humans, the artists concentrated on where the fat layers went.
Evidently, fatty tissues were important, more than the face, hair or other attributes.

Today, in a social millieu of excessive plenty, the possession of layers of fat is considered ugly and common and the most powerful humans are repelled by this and their eyes seek out slender and tall genes. Possessing many recessive genes as possible is important, too, since the rich and powerful want VISUAL TAGS TO IDENTIFY EACH OTHER aside from their obvious wealth. As in all previous eras, they contend with the problem that they, themselves, are not the ideal vision and the need to insure their children are this vision of perfection.

Many deal with this paradox by cheating. Fixing their noses, surgically removing the now unsightly fat, dying the hair, whitening the skin, the pampered poodle look is the ideal. Females, in particular, carrying the genes of these cultural tags, are quite valuable. Women without these tags must counterfit their appearance so they can tap into the wealth of powerful males who might spurn them, otherwise.

The modern world suffers from this obsession to breed visual ruling class identifying tags. Hitler was the maddest one in this regard, he carried hardly a single attribute of the ruling class stamp so he decided to literally stamp out millions and millions of humans in his quest to perfect an alpha homo sapiens, the Superman and Superwoman ruling Untermenschen.

It is no coincidence that this image of rulership coincides with the visual appearance of much of the European Norman ruling class. When oil was discovered in the Middle East, many men there ran off to find European Norman wives. The desert women who evolved through centuries of family building in that region tend very strongly towards jet black hair and natural sunscreen skin, were rejected for a while. In Asia where red or blonde hair meant someone was starving to death, for hair turns red when starving, after the European conquests, many Asians now dye their hair in order to increase their desirability.

I am predicting, as wealth and power collects in Asia, this need to alter themselves to look like a small subset of European ruling class people will fade and eventually, women will want straight, black hair instead of blonde, for example.

In the fashion world, it is nearly wall to wall tall, skinny, mainly blonde women with long fingers and necks strutting along, eyes examining the acouterments of the males who are watching them, checking them out, seeking rock stars or billionaires to latch onto and grab some of that wealth and power for their potential offspring. Short, fat women need not even think of trying for these men.

And so it goes. If civilization collapses, and this happens with shocking regularity, the short, "frumpy", darker skinned women will be triumphant since Mother Nature likes stubborn strength and the ability to keep on going even when starving to death, to hang onto fat fiercely so the mother can share it with her baby, to be protected from the capricious sun's rays, as well as strong hands and strong feet.

Throughout nature, females look for strength. And males want females who can raise a clutch or chicks or a baby. No babies=no evolution/no future.

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Comments

As I explain in (paper 5 page 6 of) my ebook at www.nodrift.com/vol_5/5.1.pdf :

“SEXUAL SELECTION THUS MOST IMPORTANT FOR HOMO SAPIENS
. . . evolutionary considerations AND homo sapiens evolving in AA Africa, coming “Out of [AA] Africa”, not “Out of [IR] Asia”, page 5, imply a corollary:

Conventions are very much a product of sexual selection. Sexual selection has thus evidently been more important than natural selection in evolution of homo sapiens, in contrast to evolution of homo erectus, where natural selection may have been more important than sexual selection.”

New to paleo-archaeological debates, I see how the field is unnecessarily diminished by the historical division between “out of Africa” and “regionalist” camps, in the Homo floresiensis discussion for example.

Human mitochondrial DNA (mtDNA)/Y-chromosome phylogeography shows very strongly that homo sapiens came “out of Africa”. But such explanation is generally too totalistic.

Both sides tend to illogically totalise, fail to mention or see that, while homo sapiens and the hominid genus almost certainly came “out of Africa”, Homo Erectus probably came out of Asia (Kohn 2006). Some homo erectus ancestors and other hominids may also have come “out of Asia”.

Kohn writes: “homo erectus materialised almost simultaneously in Africa, east Asia and a point in between . . . and that the dates do not rule out the possibility that homo erectus evolved in Asia.”

This difference between homo erectus, homo sapiens centres of endemism is not only true, it is also very telling, has those homo sapiens sexual selection implications.

REFERENCE: KOHN M. 2006. New Scientist. 2558, 1 July 2006, p35, p39.

Posted by: Peter Nielsen | September 25, 2006 at 10:43 PM

Hi, Peter!

True that many sorts of homo erectus and other hominids DID evolve independently all over the place.

But HOMO SAPIENS came out of a tribe in Africa. Whenever Homo SAPIENS met anyone who was a different species in the hominid group, they killed them!

This continues to this day which is why all the great apes are rapidly dying out. We are literally killing them or using them for medical experiments or entertainments.

Posted by: Elaine Meinel Supkis | October 14, 2006 at 12:04 AM