MEC1960

"It's always the males that have to fight over the chance to mate, whereas for females it's practically guaranteed that they'd be able to have offspring if given the chance." Yes, but you've left out 1/2 the equation - the females are always active in this too. Even when it is males fighting it is always in some sense the females actually choosing their mates. When males fight for reproductive dominance they are doing so because the female won't mate with just anyone. Sexual Selection was Darwin's other great idea (Natural Selection was the first). In most species where there is direct competition among males for mates the nature of that competition tells the females something important about the males; grizzlies wrestle, giraffe smack necks, gorillas threaten each other. Those behaviors arose because they help the females in making their decisions about mating. In most species there is no direct competition* between males so it is much easier to see the female driving the mating selection, but they are doing it as well when the males fight each other - they are making choices. *meaning fighting - most species have some kind of male-male competition

Again, in terms of biology the concept of human races is of little value. Much better to speak of populations as defined by biologists; discrete largely (that is.. not exclusively) interbreeding groups. That is because the many traits we associate with "race"; skin, hair and eye color, facial and morphological characteristics, disease resistance/risk groups, etc, exist in our species on continuums that don't allow for discrete categorization. Genes, however, are discrete units of heredity and thus it is populations of people that ought to be compared, not races. In these terms there may well be differences in cognitive abilities between populations in as much as intelligence is party due to genetics. However, unlike skin or eye color, our intelligence is not a direct result of gene expression. It is an emergent property of a complex interaction between our genes, our development and the environment in which we live. It isn't controlled solely by our genes. This is why IQ comparisons across political borders (comparing one country to another) doesn't say much about about the underlying IQ of the people in those studies. They may instead reflect differences in non-genetic influences. These are extremely difficult to untangle (the techies know this as an "NP Hard" problem). I don't think those arguing here for racial differences mean that any particular member of one racial group is more intelligent than any particular member of another, just that on average there is a difference. Biologically that is an unsupported claim because in humans racial groups have little useful biological meaning. If however the word "racial" is replaced with "population" then, although there is scant evidence of any such differences, there is at least a reasonable scientific path forward to test it. One must first define the populations to be tested, however and therein is a much bigger problem. What suite of gene expression traits impact intelligence and how do those change over time? We are very far from understanding that. In the end - I believe there is no biological support for the usefulness of race in questions of human intelligence.

That's true, StringJunky. Race *isn't* a very useful concept most anywhere. In some branches of biology (medicine and genetics, for two) it has small use but certainly it is meaningless in any large sense to the biology of our species. In social, political and religious world views it plays a vastly larger role (and as badly muddled by many) than it does in biology.

"would I throw a wrench into the works of your entire debate here if I told you that most of us Biologists and Anthropologists believe there actually is no such thing as "race?"" I am a biologist (immunology/genetics) and I disagree that we biologists think human races are myths. They do exist, but they have little biological meaning (for all the reasons we have here tried to explain to Mikemikev). Intelligence is an emergent property that is a highly complex interaction of genetics, environment and development. Race, in its simplest form, means shared genetic characters. The problem facing people like Mikemikev is that there isn't a single set of shared genetic characters such that by simply looking at those characters could you tell which race the person belonged to ...and significantly....just as you cannot tell what a person's IQ would be by looking at their genes. Currently I work in reprogramming T cells for use in autologous adoptive cancer therapies. There are distinct racial differences in the way people respond to therapies and even in the course of the disease itself. Of course there are also sex, age and familial differences too. It is in medicine where the differences between races may have a real biological basis as most medical issues are impacted by genes and those are the units of heredity. The medical community has just recently come to grips with the reality of treating differing racial groups as, depending on your ancestry, some therapies are more effective than others. ALL of these racial influences on health care are, of course superimposed upon and made more complicated by environmental, cultural and developmental influences. It is these latter which have the largest effect size, but race does as well. Human races really do exist but it's just not a very useful concept in biology except in some rare and highly specific places, most prominently in medicine (and only when very carefully worked out...so we know what we're talking about)

Sexual selection is a major driver of evolution and was one of two mechanisms first put forward by Darwin (the other being Natural Selection). It manifests itself in hugely varied ways in all sexually reproducing organisms. Even in plants; orchids are the birds of the plant kingdom in this regard - where sexual selection can yield extreme differences. In humans there is evidence of sexual selection. For example, most animals experience periods of estrus (sexually receptive behavior -called lordosis- accompanied by ovulation) that occurs often in very proscribed intervals. Humans (as well as our close cousins the orangutans and bonobos) undergo concealed ovulation - that is we do not show signs of estrus even when ovulating (though often the woman knows). This in humans and bonobos, though probably not in orangs, may be a sexually selected trait as concealed ovulation is a way to ensure that males stay around or it may be beneficial in group behaviors. Other possibly sexually selected traits in humans include large prominent mammaries in females, relative hairlessness in females, long hair on the head and face of men, facial structures, etc. Here's the thing....it is difficult to disentangle most traits from sexual dimorphism. That is there may be other reasons, examples of natural selection, for some or all of these traits. The truth is likely that sexual differences in humans are driven by a spectrum of influences from primarily sexual selection to primarily natural selection. In many birds it is obvious; a peacock's tail is a strong negatively selected trait in terms of natural selection - they cannot easily escape predators when their tails are set for display. Peahens are not under that kind of selection. It is clear that it is very strongly sexually selected trait as peacocks are willing to risk their survival to enhance their chances of reproduction. Compare that to sexual traits in humans. Is the shape and robustness of the male jaw a sexually selected trait or is it an example of natural selection? It is difficult to come up with evidence in support of either (or rather, what evidence there is supports both).

"I find it interesting that so many acknowledge that genetic factors account for a wide range of characteristics among humans and their diverse races, such as athletic ability, hair color, sweat-gland concentration, body-shape, height etc, but that somehow genetics mysteriously plays no role in intelligence." Of course intelligence is partly determined by genes though it is also largely dependent on development and the environment. No one - not anyone knowledgeable about biology or genetics- would dispute that. Our intelligence is partly dependent on the intelligence of our ancestors, just as our eye color, adult height and susceptibility to heart disease is. Intelligence is a product -an emergent trait- of biology and is thus subject to the rules of inheritance (and development and the environment). "It is silly to believe that we are all equal mentally." Of course it is, but no one is saying we are. What we are saying is that you've got your question wrong - one that carries the baggage of racism. What you and others have failed to do is to define race in a biologically meaningful way. Here is an illustration of where you fail; "That we are unequal physically is a readily noted fact-- no one has any qualms about saying that an African makes a better basketball player than a Caucasian. That we are unequal mentally is a hot potato that no one wants to touch because being labeled a "racist" ruins lives, ruins careers, and ruins your own self image." *Which* Africans are better basketball players than Causcasians? Are the Aka, Efe and Mbuti people (who average adult heights are under 5'1") better? Google images of them and tell me what race you think they are. You have made the mistake of thinking that because most African-Americans trace their ancestry to regions of Central and West Africa that all Africans look like them. They don't. The point is - there is as much genetic diversity *within* a race as there is between them. We have no -and I mean none- evidence for racial differences in intelligence. There *are* differences that are both regional and cluster in racial groups - and these differences are usually attributed to a large number of variables, including social status, wealth and family history, etc- but those differences disappear when the focus is broader.

What Mr Cuthber said... I'll add on other thing....you've got you knickers in a twist here based on a *single* sentence in a Wikipedia article! Wikipedia! It appears you may even have mis-read it, too. The sentence was referring to the first people who inhabited what is today Turkey; "It is generally agreed that the *first* Turkic people lived...". Since that time Turkey, being where it is, over the centuries has had large numbers of people moving in and out of the area such that now it is peopled by those who ancestors came from all over the region, including the Caucasus.

What you've just described is not science. It's farming. We've been doing this for 9000 years. Almost all of our agriculture is based upon the ability to use inbreeding to produce the crop or animal we want. The biggest problem with inbreeding, however, is as StringJunky alluded to - it reduces genetic variation and that limits a species ability to cope with changes. We are able to produce gigantic populations of highly inbred animals (billions of sheep, cows, chickens, pigs) and plants because we control the environmental, food, health and other pressures they would otherwise face, but such a population without our husbandry would quickly disappear. Inbreeding reduces variation and thus one can derive clonal lines (what you call "pure bloods"). This is routinely done in the lab as well as the farm and is useful if you want the reduce variables due to genetics. Genetic disorders can and do arise and persist in these clonal lines and would in any other inbred sexually reproducing organism. The main reason is that mutations occur at a constant rate (humans, like other eukaryotes, have a mutation rate of about ~1.2 x 10^-8 per site per cell division) and these mutations continually introduce new variation. It is also the case that many genetic disorders do not affect reproductive success and thus are "invisible" (or at least difficult to see) to evolution. A disorder such as ALS which arises late in life, often well past child rearing years, can persist because it is not visible to selection.

I wish you luck on your writing. Some thoughts (in no particular order) in response to your questions; 1) Neither opposable thumbs or bipedality are necessary for intelligence - read Larry Niven and Jerry Pournelle's "Footfall" for an example. 2) The vertical pupil of cats, like many predators, may well be an adaptation to hunting in low light while their prey often have horizontal pupils, presumably for greater visual coverage and scanning for predators; see Banks, Martin S., et al. "Why do animal eyes have pupils of different shapes?." Science advances 1.7 (2015): e1500391 for details into pupil shape adaptations. 3) A bony skeleton has great advantages over cartilage in terms of strength and injury repair. This is why the great majority of vertebrates have bony skeletons. 4) Pointy ears are less important to animals than *pointable* ears. That is, while shape is important, the ability to move them and having them separated horizontally by the skull - and for some animals highly dependent on sound, like owls, ears that differ in the vertical plane as well (for locating the source)- is critically important. 5) Small creatures are not more energetically efficient than larger animals - quite the opposite in fact- though they often need to consume or convert less energy overall to survive. There is a reason why warm blooded animals (especially mammals) are larger nearer the poles - the large size makes thermoregulation easier and more efficient. The down side is that a larger animal needs more food over all. 6) A slender build may be helpful for an arboreal life, but it is not required. One obligate tree-dwelling primate - our close relative the Orangutan- weighs the same as we do. Our species is more slender (and taller, called "gracile" in scientific terms) than other known human species. This is not an adaptation to arboreal life however as the human lineage left the trees millions of years before we showed up and other humans with the same ancestors, like the Neanderthals were much more robust (and had bigger brains). It is not known why our species is more gracile than other humans, but it may well have to do with our lifestyle; we are migrants. Our species moved around a lot. It may be that being gracile was adaptive to such a hard mobile life. 7) With regards to "human like" cetaceans, you might read "Galapagos" by Kurt Vonnegut. In the story the ghost of Kilgore Trout's son watches over one million years of evolutionary history as the remnants of human beings evolve into dimwitted seal-like creatures on the Galapagos Archipelago. You might get some pointers there. But the book is hilarious. Best of luck

"What do these caste systems generally entail? They vary. Typically in modern hunter/gatherer societies the castes are comprised of members who have specialized skills - hunters, warriors, weavers, laborers, fishers, etc. They can and do overlap, so these don't exactly resemble the caste system we see in agrarian societies like recently in India. They tend to be rigidly hereditary (and at times racist) but there is some overlap in skills and roles between groups. The relative importance of each caste also varies. In the modern Watta culture, for example, hunters were considered a low caste while in the San they were among the most privileged. As agriculture took root, some castes -especially the warrior and religious castes- began to take and wield the kind of power and authority we come today to know as class. "And does that mean there's a leader caste who makes decisions for the group?" The difference between caste and class can be a bit complex and subtle, but in a class system there is mobility between classes while in caste systems there is comparatively little social movement. Both systems can be hereditary, but the caste system is more rigid in this regard. Oddly, though modern hunter-gatherer groups have a more hereditary style (castes), they don't show as much reliance on hereditary power and authority as do agrarian cultures, which are almost all run by warrior/religious classes - themselves often hereditary. This may reflect the egalitarianism of a hunter-gatherer, which seems at odds with the overall caste system. Perhaps it is better to view it as pragmatism rather than egalitarianism. To be sure, it is much more common for the warrior or religious castes to be in control of a hunter-gatherer group than, say, a fisher caste but power and control in the hunter-gatherers is more tenuous and can differ from group to group. It's been a long time since I've read up on this but I think the reasoning is that because hunter-gatherer societies are dependent on highly variable resources no one kind of caste can claim authority all the time or in all places. I should point out that everything we know about the structure of hunter-gatherer societies comes from studying modern ones. With very few exceptions, these modern hunter-gatherers did not live without interaction with or influence from modern agrarian or industrial societies. One of the constant problems those who study these groups face is to try to disentangle those influences that, in many cases, are superimposed on the hunter-gatherers. This superimposition can change how their societies function, how they are structured and how they change. Always we need to be careful extending these findings to ancient human groups. It is best to let the direct evidence (via fossils and artifacts) speak for themselves.

As these were "prehistoric" there isn't much to go on. Still, we can glean some things from the artifacts and fossils left for us. Prior to the invention of agriculture, our species is likely to have existed much as recent hunter-gatherers societies did (do). That means that we lived in relatively small groups, perhaps up to 100 or so individuals but likely much smaller. In addition, these small kin-groups were likely part of much larger supergroups - perhaps of kin or anyway groups that they did not live with year round but who they were used to interacting with, trading with, warring with, from time to time. We know that there was constant contact with others because our species has a relatively low genetic diversity, indicating not only bottlenecks (one, thought to be about 75k years ago may have resulted in our species population dropping to the low 10s of thousands) but it also indicates extensive gene flow between groups. We can even map these out and get estimates for when and how human populations moved and interbred. This indicates that we were highly mobile both geographically and socially, even then. The evidence shows we lived in hunter/gatherer societies where group size was highly proscribed by resource availability. For all its attendant problems, the invention of agriculture allowed for much more intensive living as well as greater stratification and diversification of roles in the society. The rise of cities was mirrored by the rise of the ruling class and the appearance on non-food producing/procuring professions. Hunter/gatherers do have some stratification and diversity in them, but the rigors and difficulties of such a lifestyle serves to reduce their breadth - the difficulties inherent in living a hunter/gatherer lifestyle meant they could not afford to have too many specialized skills or roles. We don't know how their communities were stratified but modern hunter/gatherer cultures are built on something like a caste system - sometimes hereditary though often not. Modern hunter/gatherers tend to be more egalitarian both in the structure of their communities and the outcomes of their interactions and there is no reason to think early humans were any different. This egalitarianism and role limitation may simply reflect a solution to survival with limited resources; they couldn't afford to mess about with the kinds of functions intensive, complex societies face. There are many studies on the ethnology of modern hunter/gatherers that would be of interest to you. These groups were studied partly (largely) because they represent the style of life our ancestors led.

"Does the fact that all humans are descendants of just one man comes from the probability theory and can it be strictly proven, i.e. can the probability be calculated?" All humans alive today -and at any point in the past or future- MUST share a single male and female ancestor. When those ancestors lived changes as time goes on and they are very unlikely to have lived at the same time, or even the same millennium. This is not really the result of "probability" theory. It's basic arithmetic. Humans, like all other sexually reproducing organisms on earth, are the result of reproduction between one male and one female - this results in a pedigree that is binary and bifurcating. It is a mathematical certainty that at any point in time all members of a sexually reproducing species share a single male and a single female ancestor.

H. heidelbergensis is not much different than H neanderthalensis, except (as you point out) for some secondary characters such as a sloping forehead, pronounced brow and smaller chin in the Neanderthals. Neanderthals had more robust skeletons and musculature and had bigger brains than either heidelbergensis or sapiens. H. sapiens differs from both species by being taller and more gracile. We also have different secondary characters that are much more pronounced with comparison tot he Neanderthals but also differ with heidelbergensis such as a flatter face, more robust chin, almost no brow and a high vaulting cranium (though with a lower capacity than the Neanderthals). What accounts for these differences? Since no other human species exists today we can only guess. Perhaps our smaller, more gracile frame is an adaptation to a more migratory lifestyle. It does seem that our species moved around a great deal more than the Neanderthals. Differences in the chin (and thus the jaw) may reflect differences in diet -there is some evidence for this. Differences in the shape of the face and skull may reflect differences in the size and function of the different brains. Though Neanderthals had bigger brains it may be that their fore brain function wasn't as important to them, thus though overall their brains were bigger, their fore brains may have been smaller and this resulted in a more sloping forehead - we do not have any Neanderthal brains to know for sure. It may well be that the Neanderthal brain was better suited for a sense of smell and thus their facial structures were adapted for that; a large prognathous face may have allowed for more acute sense of smell. On the other hand, some or all of these characters may be the result of sexual selection - it may be that a certain face or head shapes were preferred by either males or females (or both). It's also possible that some of these differences may be mere spandrels and have no adaptive purpose.

The term also ignores drift at the phenotypic level and neutral theory at the molecular level. Darwin was right - natural and sexual selection are the main drivers of evolution and since the raw material of evolution is mutation, it can be said to be like trial and error solutions. However, we now know that there are stochastic drivers of evolution, such as drift and neutral theory.

Identical twins share exactly the same DNA, but we are not the sum of our genes. Our genomes are not like blueprints, they are more like a recipe. We are the result of a complex interaction between our genes, development and the environment; our genes only describe the boundaries of who we can be, (I will never be a 4 foot tall Chinese woman, for example), not ultimately what we become. This is to say that although they share exactly the same genes, identical twins are identical in only that sense. They can differ in physical, physiological, emotional and psychological traits, including sexual preferences.