This early fossil hominid was initially placed within the Australopithecus genus, with a new specific epithet - ramidus (from the Afar word "ramid", meaning "root") [White, et al, 1994]. Tim White and associates have subsequently reassigned the hominid to a new genus, noting the apparently extreme dissimilarities between ramidus and all other known Australopithecines. They proposed Ardipithecus (from "ardi", which means "ground" or "floor" in the Afar language) to be the genus [White, et al, 1995].
GEOLOGICAL SETTING
The initial and most extensive publication [White, et al, 1994] concerning Ardipithecus. ramidus specified that 17 hominid fossils had been located by the end of 1993. These specimens were retrieved from a cluster of localities West of the Awash River, within the Afar Depression, Aramis, Ethiopia.
Hominid and associated fossil faunas, including wood, seed and vertebrate specimens, were found entirely within a single interval overlying the basal Gaala Tuff complex, and beneath the Daam Aatu Basaltic Tuff (these volcanic strata have produced dates of 4.389 and 4.388 million years, respectively) [Renne, et al, 1999]. This definitively places all Ardipithecine specimens just shy of 4.4 million years ago.
Additionally, the associated strata were most likely produced within the context of a heavily forested, flood plain environment. Evidence for this conclusion was derived from representative non-human fossil remains, particularly from those species whose present-day analogues are environment-specific.
Curiously a flood plain is not always flooded, nor is seasonal flooding necessary to be classified as flood plain. The specification for heavily forested could easily be more descriptive of very occasionally flooded plains.
Living in these kind if areas could just mean that the ground is easier to dig for finding tubers and that there are nut and fruit bearing trees and bushes growing in the fertile soil with a relatively high water table.
Then we have the consideration of anatomy (ibid):
quote:ANATOMY
A morphological description of the initial, mainly dental, fossil remains of Ardipithecus ramidus was published by White et al, 1994. The physical attributes of this hominid show a range of primitive traits, which are most likely character retentions from the last hominid/chimpanzee ancestor. At the same time, some hominid innovations are equally apparent. The currently known traits of Ardipithecus ramidus, in general, can be placed within two categories: ape-like traits and Australopithecine-like traits.
Much of the dentition is ape-like and this hominid most likely had a significantly different dietary niche than did later hominids. A small canine-incisor to postcanine dental ratio, typical of all other known hominids, is strikingly absent in Ardipithecus ramidus. In addition to the presence of a relatively large anterior dentition, tooth enamel is thin. Though slightly greater than in teeth of modern chimpanzees, enamel thickness of A. ramidus is extremely thin by hominid standards.
Premolar and molar morphology also point to niche affinities with the great ape ancestors. Strong crown asymmetries, in particular enlarged buccal cusps, characterize the upper and lower premolars. Additionally, an ape-like molar shape prevails. The length (in the mesiodistal plane) to breadth (in the buccolingual plane) ratio, which is roughly equal to 1 in later hominids, is much greater in A. ramidus.
Some important derived features, link Ardipithecus ramidus with the Australopithecines. Hominid-like canines are present. These are low, blunt, and less projecting than the canines of all other known apes. Upper and lower incisors are larger than those of the Australopithecines, but are smaller than those of chimpanzees. This character state can thus be considered transitional between apes and Australopithecines. Additionally, the lower molars are broader than those of a comparably-sized ape. This trait, too, approaches the common hominid condition.
Finally, something can be said of the skeletal anatomy and how it relates to the potentiality for bipedalism in A. ramidus. Pieces of the cranial bones that have been recovered, including parts of the temporal and the occipital, strongly indicate an anterior positioned foramen magnum. The fact that the skull of A. ramidus rested atop the vertebral column, rather than in front of it, suggests that if this creature was not bipedal in the modern sense, it at least had key adaptations toward a similar end.
Scanty postcranial remains (most significantly, a partial humerus) indicate that A. ramidus was smaller in size than the mean body size of Australopithecus afarensis. However, this particular estimate falls within the range of variation of A. afarensis.
That puts it intermediate between ape and Australopithicus, and thus more like apes in ability to swim. It also seems to me that the skull placement on the spine argues against an aquatic ape adaptation, as now you have to lift your head more to breath, whereas most aquatic or amphibious animals are arranged to facilitate breathing.
Now, one of you should present some evidence about the "floodplain" of eastern Africa ~5 Mya, because only case-specific evidence is going to resolve this issue.
All I can find is reference to the ethiopian uplift and drying out of the climate ~4Mya.
On a side note, my feet are not adapted to swimming at all. They don't fold back enough to act as flippers, and they are skinny (like those old footprints) and I can get more propulsion from one hand than I can get from both feet kicking vigorously (a way to get exhausted).
The first bipedal apes were virtually defenseless. A prey that can't accelerate to 45 mph or burrow or fly up a tree is lunch to a leopard or lion.
Curiously, a test of manhood for the Massai was to go out and kill a lion single handed, with just a shield and a spear. Strangely, Chimpanzees have been filmed defending their group from a lion, using sticks.
Again, we easily swim and dive.
And you still have not explained why crocodiles are not a problem when lions are.
Flood plains are good habitat for finding edible plant materials, roots, tubers, fruits, nuts, because the ground is fertile. A wooded floodplain also provides a diverse habitat for small fauna that can be killed with sticks (as chimpanzees have done).
I don't see any evidence of shell middens etc that would indicate a use of the marine environment, as we see later with some early Cro-Magnon (sapiens) evidence.
I would not be surprised to see early hominids taking advantage of the opportunities of marine life to supplement their diet, but I do not see it being a formative behavior.
There is a Borneo primate called the Proboscis Monkey. This monkey swims and dives very well. It also will wade bipedaly, mother holding her youngster on her hip. in deeper water, the baby climbs on swimming mom's back. This is an obvious adaptation to a wet environment. It's been done, and the example is here. No one has filmed this wondrous creature under the water that I know of.
Odd indeed, and if you saw it away from the water, you may never know it's secret. It has long legs, that are very limber, being able to swing in line with the spine so it can easily and efficiently propel the monkey forward in the water and facilitate wading. It's fir is dense, and runs downward. ...
I see you're back hyping the aquatic ape conjecture again.
You just cannot escape this little hominid worked his way over thousands of miles of coastline to reach Indonesia. They did it on abnormally long flat feet. They worked the shoreline. Slam dunk!
And this explains why Polynesians are better adapted to living in the water than Tibetans, with their webbed feet and hands, their eyes adapted to see underwater, and their lungs adapted for the ability to hold their breath for extended periods ... except they aren't. Unfortunately (for you) Homo floresiensis is off topic on this thread.
The real question is not why humans seem to lack fur (our skin is hairy, and just as hairy as chimps when placed on the scale of mammals size versus hair follicle density), the question is why there is a sexual dimorphism in the hair development patterns of humans.
Cursorial hunting does not explain this - especially when the hunters are the hairier sex.
The Aquatic Ape conjecture does not explain this - again the hunters are the hairier sex.
You need to look at the hair development pattern to understand why there is a difference, and once you have explained that difference the reason for the hairless appearance of humans becomes clear.
Hair development occurs in stages, in humans and in other apes and mammals, and the first stage is called Lanugo hair, and this is the fine hair that covers a fetus, and that normally falls out before birth or shortly afterward. The next stage is vellus hair, which is also fine and is the hair commonly found on children. Terminal hair is, as the name suggests, the final stage of hair growth. The hair on your head, pubic hair (after puberty), armpit hair and the beards of men are typical examples of terminal hair on humans.
Male humans have predominantly much more terminal hair than females, and this hair is seen on arms, chest, backs and legs, in a wide range of distributions.
Female humans have predominantly vellus hair except on the head, pubic area and armpits, and this pattern is consistent for females.
This conformity in females compared to the extreme variation in men, suggests that the operating selection for lack of visible hair is occurring in the selection of females.
It is considered abnormal for a woman to have hair similar to men. There is a medical term to describe this condition in women, while there is no medical condition that describes men as having "female pattern" hair. The variation we see in men is greater than this "abnormal" condition in women, and there is general gradations throughout the population between the hairiest males and the "hairlessist" males.
Females don't grow terminal hair on their bodies because the hair development pattern is arrested while they still have the childhood vellus hair pattern. This adequately explains why humans appear to have less hair: selection has caused the development of hair to terminal hair to be arrested. The next question is why did selection make this arrested development to be better suited for survival or reproduction.
As survival selection does not distinguish be sexes, it becomes clear that sexual selection is operating. There is further evidence that this selection is still occurring, in the shaving behavior of women compared to men, and in the preponderance of shaved bodies in porn (as an indicator of sexual attractiveness).
Note that terminal hair, other than on the head, normally grows after puberty - after becoming able to reproduce - and there is a common observation in organisms, that once reproduction is reached, the organisms stop body development, "arrested" at the stage of development where they become able to reproduce.
Conclusion: sexual selection for young appearing women has driven selection of adult women with childlike hair patterns, resulting in arrested development of hair at the vellus stage in women. Such selection is not operating on males, hence the wide variety in patterns of male hair and the much less degree of hairlessness in males compared to females. The hairlessness of males is a result of shared genes with women, genes that are affected by the selection in females and then shared with the males.
I don't think claiming we all have just as much hair as chimp is constructive in this debate. Having peach fuzz is what makes us look naked.
Except that it shows that we have not lost hair, only that the hair we have is arrested at a level of hair development normally found in children, and thus it explains the "peach fuzz" hair that is universal in women and visible in men wherever terminal hair does not grow.
Aquatic species, on the other hand, don't have "peach fuzz" if they don't have terminal hair - they either have fur or they don't.
There is also no example (I am aware of, anyway) of such sexual dimorphism in the hair\hairless patterns of a single aquatic species.
Thus the apparent hairlessness of humans does not match the fur\hairless pattern of any aquatic mammals.
I think it is getting harder for folks to turn their shoulder to the semi-aquatic ape.
Only if you ignore all the evidence that contradicts this concept. What you "think," curiously, has no effect whatsoever on the reality around you, while your continued denial of contradictory evidence could be indicative of Delusion:
So how do you explain the dimorphism in hair patterns between males and females in humans and the lack of sexual dimorphism in hair patterns between males and females in marine mammals from heavily furred seals to bare whales.
If you cannot explain the dimporphism, then your conjecture cannot explain the apparent hairlessness of humans, no matter what your conjecture involves.
In other words, your conjecture is dead in the water.
Olympian swimmer have noted faster times swimming nude.
It is common practice for swimmers to shave their entire bodies in order to remove the "peach fuzz" that does, indeed, cause drag.
The US Navy has spent a considerable amount of tax dollars investigating drag on ships and submarines, they have modelled the skin of sharks and whales, but they have not modeled "peach fuzz"
Racing sailboats have also spent a lot of time and effort at reducing drag on their vessels, including (but not limited to) scraping off the "peach fuzz" that grows from some forms of algae.
So how do you explain the dimorphism in hair patterns between males and females in humans and the lack of sexual dimorphism in hair patterns between males and females in marine mammals from heavily furred seals to bare whales.
If you cannot explain the dimporphism, then your conjecture cannot explain the apparent hairlessness of humans, no matter what your conjecture involves.
In other words, your conjecture is dead in the water.
I am reading your messages very well, every one full of arrogant assertion and devoid of evidence, and completely ignoring the evidence that shows your argument to be irrelevant, refuted, falsified.
I predict that soon you will see a post from an Admin, telling you to substantiate your claims with evidence, rather than adding more assertions. They may also advise you to deal with the issues that people raise, rather than repeat discredited assertions.
Question: why can't you explain the sexual dimorphism?
'Missing link' fossil seal walked Writing in the journal Nature, scientists suggest the 23 million-year-old proto-seal would have walked on land and swum in fresh water.
Curiously, I don't count a factor of 4 as infinity - if it took 23 million years to get from this shore living walking mammal to a seal: we don't know what they looked like 6 million years later, but I'll bet they were more seal-like than otter like.
What I see is absolutely NO evidence of any aquatic adaptation in humans, especially humans that have lived along shores long after H floresiensis made it to this island.
Our line split from Homo Habilis long before H Florensius found the island of Flores. We had the next 250,000 years to be modified into our present state. It isn't unusual at all for a separated population to acquire some regressive traits, like more hair.
So why haven't the hominids that continued to live along sea-shores not become more adapted to the aquatic existence if we have regressed?
You argue that we've had time to regress in 1/4million years, but our ancestors did not have time to develop special adaptations like seals have over 6 million years? That's a factor of 24 ... special pleading anyone?
Humans evolved from an ape species that existed about 6 million years ago (sometimes called "Pan prior"). About 2.5 million years ago, the common chimpanzee and the bonobo became separate lineages, as did bipedal woodland apes (e.g., Australopithecines) and our Homo lineage (in white). About 1 million years ago, both the gorilla and chimpanzee lineages split into east and west subspecies because of ice age droughts. Extinctions are shown by terminated bars; only arrows represent extant species.
2) Another model is needed.
Woodland dwelling bipedal apes fits the fossil evidence. Similar habitat and behavior are again seen in Bonobos
Body hair is one of the most important features of the mammal thermoregulatory system. Hair can act as an important heat retention and heat prevention device in mammals. By trapping a layer of dead air against the skin, a layer of hair can act as an extremely efficient insulation, reducing the rate of convective heat loss to the environment. However, this exact same system acts as a way to prevent heat gain from the environment by the same principle; by using this layer of dead air to reduce the rate of convective heat gain from the environment to the skin. Besides insulation, the layer of hair on mammals is important in reducing the radiation from direct and indirect sunlight, and can thus act to reduce heat gain from the environment in two ways.
If loss of hair was an important variable in thermoregulation then we would expect {evolutionary pressure \ natural selection} to show a broad trend of hair thickness variations that could be correlated with the need to {retain\dissipate} heat.
We do see this. From the same source, here discussing the need of larger bodies to {retain less \ dissipate more} heat due to the increase in volume as the cube but skin area as the square of a size dimension:
The obvious solution to this situation is decreased body hair with increasing body size, which is exactly what is seen in anthropoids. When the number of hair follicles present in species per unit of area is compared with body size, all primates (including humans) fit along a regular log linear regression line, along which the density of hair per unit of area decreases as body size increases. Species like chimpanzees and gorillas have relatively fewer hair follicles per unit area of skin compared to the smaller monkeys. Humans fall along this line, and have a relative hair density almost the same as seen in chimpanzees, gorillas and orangutans.
To drive this point home, the number of hairs on the human body are precisely what they should be for the human body size. We are not displaced on the scale. There is no special loss of hair required for thermoregulation, and thus there is no special mechanism needed to provide for the loss of hair: no mutation is needed for the explanation of amount of human body hair.
Thus there is no loss of hair, humans have as many hair follicles per unit area as apes have when compared on a scale with body size. They do not deviate from the curve of the other apes. The number of hair follicles is normal for an ape of our size.
What we have is the arrested development of hair from childhood patterns to adult patterns, a change that occurs with becoming capable of reproduction. Such arrested development is common in species where they evolve to be capable of reproduction before becoming fully developed.
4) It is a fact the barer we are, the faster we swim.
It is a fact that every furred marine mammal can swim faster than humans, from sea otters to harbor seals to elephant seals. Thus the fact is that we are NOT adapted to swim, unlike otters and seals. Their adaptations to swimming have nothing to do with furriness, and thus furriness on it's own is neither here nor there when it comes to swimming ability.
It is a fact that shaving off all hair makes humans faster swimmers, thus adaptation for swimming would remove all hair equally - no sexual dimorphism, no long tangled curly head hair, no hair at all.
The fact that you cannot explain the sexual dimorphism of humans with swimming means that it is a falsified conjecture. A valid hypothesis explains ALL the known evidence and is NOT contradicted by any known evidence. The bi-pedal forest dwelling ape with sexual selection explains the evidence of gait, of sexual dimorphism, and it matches the distribution of all fossils, not just those alone shores.
5) H Habilis migrated by water to far shores. So says the science community.
And also inland, away from the shores. We also see Polynesian people no more adapted to a water swimming life-style than Tibetans. What you are employing is the post hoc ergo propter hoc fallacy coupled with ignoring the evidence of H.habilis living inland, and in virtually complete denial about sexual dimporphism.
There is no valid argument chimp fur is fine for a swimmer. That is nonsense.
Which is the argument from incredulity, plus completely ignoring the swimming ability of otters and seals.
All you are doing is cherry picking evidence to suit your conjecture and reveling in Confirmation Bias:
So once again, I point out that your continued ignoring of the evidence of sexual dimorphism shows that your conjecture is false. From Message 133
So how do you explain the dimorphism in hair patterns between males and females in humans and the lack of sexual dimorphism in hair patterns between males and females in marine mammals from heavily furred seals to bare whales.
If you cannot explain the dimporphism, then your conjecture cannot explain the apparent hairlessness of humans, no matter what your conjecture involves.
In other words, your conjecture is dead in the water.
Your inability to address the issue of sexual dimorphism is evidence of Cognitive Dissonance
You cannot explain the sexual dimorphism, so you don't even talk about the issue. This is denial of the reality that sexual dimorphism is more of the issue than the actual amount of hair on humans. Male humans have hair that varies from ape-like to female like, while females have predominantly arrested juvenile hair patterns of vellus hair.
If adaptation to swimming were happening that the hunter should be the fastest and most powerful swimmer, and as a result should also be the sex with the least visible hair. This is exactly opposite of the evidence.
Let me repeat: it is exactly the opposite of the evidence. Thus the conjecture is invalid.
8) Certainly, the after Habilis path to H Sapiens would bring changes too.
Which is just saying that evolution will occur, not that there will necessarily be adaptation for or against aquatic ability. This is known as a non-sequitur fallacy.
Why do we have smoothing subcutaneous fat?
For thermoregulation. Why do we have sweat glands? Whales don't. Seals don't. Do you realize that every piece of evidence that you have cherry-picked is countered by pieces of evidence that you have ignored?
Confirmation Bias Cognitive Dissonance Denial
If you cannot explain the dimporphism, then your conjecture cannot explain the apparent hairlessness of humans, no matter what your conjecture involves.
quote:Sexual dimorphism is the systematic difference in form between individuals of different sex in the same species. Examples include color (specifically referred to as sexual dichromatism), size, and the presence or absence of parts of the body used in courtship displays or fights, such as ornamental feathers, horns, antlers or tusks.
Female (left) and male Common Pheasant, illustrating the dramatic difference in both color and size between sexes.
The question is, why does the female hair pattern differ so markedly from the male pattern IF selection is for less hair in general?
If selection was for less hair in general, then the selection would act on the species independent of sex, and both would have the same amount of less visible hairs.
When one is suffering from wet hypothermia ...
... it just proves that humans are NOT adapted to an aquatic lifestyle. Seals in the arctic don't get hyperthermia, nor do furless whales.
You are still engaged in cherry picking your evidence with confirmation bias, and ignoring the real problem for you conjecture:
Why is there a difference in the hair patterns of men and women? Why are women universally endowed with the arrested velus hair pattern? Why do males vary from hair similar women and hair similar to other apes?
Why is there little variation in women? Why is the mean value for women all the way to one end of the available spectrum for hair development?
Why is there a lot of variation in men? Why is the mean value for men in the middle of the available spectrum for hair development?
Why is it, that the apparent hairlessness of women needs to be enhanced even further by artificial means, and why is it done for mating and not for swimming?
Please explain each of these questions with aquatic adaptation.
""""nowhere does it state that h. habilis ever left Africa. A map inclued with the article shows the route taken by H. erectus but shows that H habilis stayed in the area between Olduvai Gorge and Lake Turkana.""""
type [qs]quotes are easy[/qs] and it becomes:
quotes are easy
or type [quote]quotes are easy[/quote] and it becomes:
quote:quotes are easy
also check out (help) links on any formating questions when in the reply window.
Except for one thing. H Florensis is very much the same as H Habilis. Comparing skulls, the similarity is striking.
How about when you factor in skeletal height? What is remarkable about H.floresiensis is the small overall size as well as the small braincase
quote:In addition to a small body size, H. floresiensis had a remarkably small brain. The type specimen, at 380 cm (23 in), is at the lower range of chimpanzees or the extinct australopithecines.[1][5] The brain is reduced considerably relative to this species' presumed immediate ancestor H. erectus, which at 980 cm (60 in) had more than double the brain volume of its alleged descendant species.[5] Nonetheless, the estimated brain to body mass ratio of LB1 lies between that of H. erectus and the great apes.[19] ... Recent research of Lyras et al.,[15] based on 3D-morphometrics, shows that the skull of LB1 differs significantly from all H. sapiens skulls, including those of small-bodied individuals and microcephalics, and is similar only to the skull of Homo erectus.
Brain size alone is not indicative of relationship, rather it is the overall pattern that is consistent with H. erectus rather than H. habilis.
Compare the shape of the skull between these pictures:
Figure 1.4.4. Fossil hominid skulls. Some of the figures have been modified for ease of comparison (only left-right mirroring or removal of a jawbone). (Images 2000 Smithsonian Institution.)
(A) Pan troglodytes, chimpanzee, modern (B) Australopithecus africanus, STS 5, 2.6 My (C) Australopithecus africanus, STS 71, 2.5 My (D) Homo habilis, KNM-ER 1813, 1.9 My (E) Homo habilis, OH24, 1.8 My (F) Homo rudolfensis, KNM-ER 1470, 1.8 My (G) Homo erectus, Dmanisi cranium D2700, 1.75 My (H) Homo ergaster (early H. erectus), KNM-ER 3733, 1.75 My (I) Homo heidelbergensis, "Rhodesia man," 300,000 - 125,000 y (J) Homo sapiens neanderthalensis, La Ferrassie 1, 70,000 y (K) Homo sapiens neanderthalensis, La Chappelle-aux-Saints, 60,000 y (L) Homo sapiens neanderthalensis, Le Moustier, 45,000 y (M) Homo sapiens sapiens, Cro-Magnon I, 30,000 y (N) Homo sapiens sapiens, modern
Does H. floresiensis match better to (D), (E), (F), (G) or some other skull? If I had to pick on skull alone and only using these pictures, I would pick (G), based on the flat face, the brow ridges and the relative size of the braincase to the face. Curiously this is from the site of the first evidence of of erectus outside africa:
quote:The Plio-Pleistocene site of Dmanisi, Georgia, has yielded a rich fossil and archaeological record documenting an early presence of the genus Homo outside Africa. Although the craniomandibular morphology of early Homo is well known as a result of finds from Dmanisi and African localities, data about its postcranial morphology are still relatively scarce. Here we describe newly excavated postcranial material from Dmanisi comprising a partial skeleton of an adolescent individual, associated with skull D2700/D2735, and the remains from three adult individuals. This material shows that the postcranial anatomy of the Dmanisi hominins has a surprising mosaic of primitive and derived features. The primitive features include a small body size, a low encephalization quotient and absence of humeral torsion; the derived features include modern-human-like body proportions and lower limb morphology indicative of the capability for long-distance travel. Thus, the earliest known hominins to have lived outside of Africa in the temperate zones of Eurasia did not yet display the full set of derived skeletal features.
Have you considered how those morphological (ie body shape) features match those of H. floresiensis?
Wiki again:
quote:William L. Jungers of the Stony Brook University in New York compared the low twist of the arm bone of H. floresiensis to the similarly small humeral torsion of an early hominid from Dmanisi in Georgia,[46] usually designated as Homo georgicus. ...
Note: the Dmanisi find is on a hilltop, not a coastline.
Enjoy.
PS - scientific nomenclature capitalizes the genus and lowercases the species, thus H. erectus is correct and H. Erectus is not.
In addition, H. floresiensis is named after the island where they were found: "It was named after the Indonesian island of Flores on which the remains were found" ... so the name is floresiensis.
H Habilis, despite it's small brain, was quite handy. Interesting H Georgicus individuals were found way up in the old USSR. I instantly got this vision of these guys looking out upon the steppes, and muttering, "We ain't in Africa anymore," just before their demise. These archaic heroes fit Japanese movie scripts of the unsung warrior very well.
Yes, what I have seen is that human intelligence has increased by two methods: an increase in sheer brain volume, and an increase in the rippling of the brain surface. Both of these increase surface area, and studies show that it is surface area that is critical to intelligence - it's where the thoughts occur. Thus a small size brain in today's population is not mentally handicapped, while a person with a smooth surface brain is - our brains are incredibly rippled.
You have to wonder what these guys were doing there, and why they are lonely in the fossil record. They are thought derivative from H Habilis, as is most likely H Florensius. I don't think H Erectus ever played a part in our evolution. H Habilis, if H Florensis is their kin. was long lived and successful.
I sometimes wonder if less fit hominid populations were driven from the homeland by more dominant (new?) populations, and then stumbled on the rest of the world. The new species drive the old species away. This would explain the primitive features in the Dmanisi and Flores Island skeletons.
I agree with you on H.erectus and H.saps being cousin species at best. I also think that H.erectus preceeded H.saps out of africa, and were later over-run by the H.saps in much the same way that we are cousin species to H.neander and over-ran them. I've seen mention of this in the literature.
With that scenario though, it is also reasonable to me that H.floresiensis could descend from H.erectus and also be a cousin species.
Unfortunately, we don't have feet fossils. That would clear up a lot of questions. I found I am not alone in thinking H Habilis started the nudist trait. I got this from Wikipedia:
(Such traits as noticeable whites in the eyes, smaller hairs resulting in exposed skin, and a naked appearance remain theoretical.)
I'll go out on a limb: I strongly believe the naked appearance evolved in the woodland forest environment back at the beginning of the divide from chimpanzees. See Message 65 and the issue of enabling mechanisms.
quote:Given this environment, substantial {apparent bareness} could develop without jeopardizing survival through overheating. This would indicate that the primary concern in this environment would be to prevent heat loss rather than getting too hot, at least during the initial stages.
A cool shaded environment enables the development of bareness while only having to provide alternate heat retention mechanisms, and not have to provide both retention and dissipation.
Our cardiovascular system is able to cope with a significant range of temperatures by regulating the flow of blood to the skin surface or shutting it down, so this would enable sexual selection of apparent bareness to occur without threatening survival of the species. Such selection would also be sufficient to divide human populations from chimpanzee populations.
quote:One advantage of the vascular system is that it works for both heat retention and cooling, thus it is best able to replace both those functions lost with hair reduction, especially for daily fluctuations where a fairly rapid response would be needed. The disadvantage is that it is not as capable of modulating extremes of heat and cold as hair would be.
Another heat retention system common to many mammals is a thicker layer of subcutaneous fat. This layer exists in all primates, but is most developed in humans. ...
...
If anyone doubts the ability of these mechanisms to provide sufficient protection from hypothermia (not too cold), then consider that when the Beagle reached the area of Tiera del Fuego at the south end of South America, that the crew were welcomed by nearly naked natives while Darwin and the others froze with the clothes they had on:
On one occasion Darwin and crew were near a good size fire and still quite cold, while the aborigines were some distance away and perspiring heavily. Charles noted this with great interest.
(same broken link on thermoregulation, unfortunately).
Thus the increased subcutaneous fat in humans enabled survival in colder environments OR it allowed the further reduction of hair development by sexual selection.
Thus I can posit sexual selection as the driving force for apparent bareness, enabled initially in the wooded forest environment by the lack of extreme temperatures year round, and then enabled by selection for increased subcutaneous fat as the bareness increased in area. This gives us "naked" bipedal apes pre-adapted to move into the savannah, where the sweat mechanism was further developed from the already existing Eccrine glands - glands that show up in similar distributions in chimps and gorillas, but not in other apes, suggesting this distribution occurred before the human\chimp\gorilla split. See Message 70.
Interestingly, the initial purpose of eccrine glands is to keep bare skin supple and soft, so the existence of these glands on chest areas of humans\chimps\gorillas would indicate an ancestor with a bare chest. Note that there is also matching evidence of bareness in gorilla males and in lactating females chimps and gorillas, so it may be that selection for some bareness patterns occurred even earlier than I have posited.
This, of course, makes the aquatic ape conjecture unnecessary, even if it were capable of generating sexually dimorphic hair distributions ... (which I'm still waiting to see some explanation of)
the 300 is the pixelwidth of the thumbnail, thumbnails are always centered and you can post a large picture but have it take up a small part of the post with this feature. The above example becomes
... and outside quotes.
You can usually copy and post the link (as I did above for the imageshack website. For long urls you'll need to do a little more:
[url=http://www.sciencedaily.com/releases/2009/05/090506144307.htm]'Hobbits' Couldn't Hustle: Feet Of Homo Floresiensis Were Primitive But Not Pathological[/url]
A detailed analysis of the feet of Homo floresiensis”the miniature hominins who lived on a remote island in eastern Indonesia until 18,000 years ago”may help settle a question hotly debated among paleontologists: how similar was this population to modern humans?
A new research paper, featured on the cover of the May 7 issue of Nature, may answer this question. While the so-called "hobbits" walked on two legs, several features of their feet were so primitive that their gait was not efficient.
But a number of recent analyses of the skull, face, and wrist have found many unusually primitive features among the "hobbits" that are more similar to chimpanzees and Australopithecus, suggesting that the Flores inhabitants represent a remnant population of early hominins.
The anatomy of the foot described in the new paper might finally answer the pathological modern vs. primitive population question. Although the foot is characteristic of a biped”being stiff and having no opposable big toe”many other traits fall outside of the range for modern humans. The H. floresiensis foot is very long in proportion to the lower limb and considerably more than half the length of the thighbone; modern human feet are relatively shorter at about half of the femur's length. The stubby big toe of the hobbits is another primitive, chimp-like trait. But the pivotal clue comes from the navicular bone, an important tarsal bone that helps form the arch in a modern human foot. The "hobbit" navicular bone is more akin to that found in great apes, which means that these hominins lacked an arch and were not efficient long-term runners.
If the foot of H. floresiensis is 30% bigger that a proportional H. sap (or H. erectus) which are 30%+ bigger than H. floresiensis ... could it not be that the foot is retained while the rest became smaller?
Are you Jim Moore or do you know him? Just curious (that's me in the first picture)
Enjoy.
ps -- still no answer on the sexual dimorphism eh?
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