Evolution helped turn hairless skin into a canvas for self-expression

Feb 17, 2013

(Phys.org)—Hairless skin first evolved in humans as a way to keep cool—and then turned into a canvas to help them look cool, according to a Penn State anthropologist.

About 1.5 to 2 million years ago, , who were regularly on the move as hunters and , evolved into nearly hairless creatures to more efficiently sweat away excess body heat, said Nina Jablonski, Distinguished Professor of Anthropology. Later, humans began to decorate skin to increase attractiveness to the opposite sex and to express, among other things, group identity.

"We can make a visual impact and present a completely different impression than we can with regular, undecorated skin," said Jablonski, who reports on her research today (Feb. 16) at the annual meeting of the American Association for the Advancement of Science in Boston.

Over the millennia, people turned their skin into canvases of self-expression in different ways, including permanent methods, such as tattooing and branding, as well as temporary ones, including cosmetics and body painting, according to the researcher.

Jablonski said both use forms of skin decoration to become more attractive to the opposite sex. Women, for example, may use makeup to increase the size of their eyes, a cue that is considered attractive in most cultures. Males in some cultures also use skin decoration as a way to bring out to appeal to women, or to look more menacing and warrior-like.

"We can paint a great design on our bodies and use those designs to send all sorts of messages or express group memberships," said Jablonski.

While parents may still fret that their children are choosing tattoo designs frivolously, Jablonski said people have traditionally put considerable time and thought into the tattoos.

"Usually it is something with deep meaning," Jablonski said. "When I talk to people about their tattoos they, tell me they've spent months or years choosing a design that is incredibly meaningful and salient to them."

Prior to the evolution of mostly naked skin, humans were furry creatures, not unlike chimpanzees are now, Jablonski said. Skin decoration would not be possible if humans were still covered with fur.

Studying skin is difficult because it can be preserved only for a few thousand years, unlike bones and fossils, which last millions of years.

Jablonski said that she and other researchers based their estimate on when humans evolved hairless skin on the study of the fossil record and an examination of the molecular history of genes that code proteins that help produce skin pigmentation.

"We find a lot of evidence of when humans began to lose hair based on molecular genetics," said Jablonski.

Humans are the only primates that are essentially hairless, although aquatic mammals, like whales and dolphins, have no hair. Prior to the idea that humans evolved hairlessness as a mechanism to cope with body heat, some researchers believed that hairlessness resulted from evolution from a common aquatic ancestor, Jablonski said. However, the theory, often referred to as the aquatic ape theory, does not match the genetic, fossil and environmental evidence, she said.

While it is difficult to exactly say when humans began to decorate their skin, Jablonski said that some of the earliest preserved shows signs of tattooing.

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alfie_null
3.7 / 5 (3) Feb 17, 2013
While parents may still fret that their children are choosing tattoo designs frivolously, Jablonski said people have traditionally put considerable time and thought into the tattoos.

Children (teenagers) are submerged in a sea of hormones that affect their ability to make rational decisions.
JRi
1.8 / 5 (5) Feb 17, 2013
And if they haven't happen to become hairless, they would have cut braid, and colored their hair like crazy.
verkle
1.3 / 5 (16) Feb 17, 2013
There is no scientific evidence that evolution changed anything. It is all 100% postulation. What instead we are looking at is how God created us. Amazingly different than the animals. And all for a purpose.

True science is a study of and a trying to understand this creation.

Claudius
4.6 / 5 (9) Feb 17, 2013
Amazingly different than the animals. And all for a purpose.

True science is a study of and a trying to understand this creation.



Amazingly similar to animals. In fact, we *are* animals. What else did you think we are? Plants? Fungi? Viruses?

IF God created us, he made us animals.
Torbjorn_Larsson_OM
5 / 5 (5) Feb 17, 2013
There is as of yet no agreed upon biological explanation for our hairlessness, unless I am mistaken.

Looking at where we keep hair, it seems to me the simplest explanation is sexual selection, something we know from genetic studies have been a major force in humans. That would go hand in hand with body patterning as its (sexual!) appeal would enforce and fixate hairlessness.

**************
Creationists shouldn't comment on science, it is hilarious and helps makes deconverts from religion, see Dawkins's Convert's Corner.

Biology and its observed basic process of population change is a science accepted by all scientists. And of course we _can't_ study ideas ("creation"!?) that we know from observation hasn't happened.
JVK
1 / 5 (7) Feb 17, 2013
Nutrient-dependent pheromone-controlled reproduction has been studied across species. It is the only model for adaptive evolution. The fact that random mutations are excluded as cause threatens non-believers so much that they run and hide, or insist that the biological facts are being misrepresented. That's what's hillarious! Natural selection is for nutrients; social and sexual selection are genetically predisposed and pheromone-controlled. It's the bottom up / top down link from genes to behavior and back that attests to Creation, since mutations can't work from the bottom up and from the top down at the same time throughout the life of any organism and the development of its behavior during times when the behavior must be adjusted to the sensory environment (i.e., even in animals with no skin to decorate). The hairless skin canvas is simply more nonsense tied to the standard "Just So" stories of evolutionary theorists.
Jonseer
4 / 5 (4) Feb 17, 2013
There is no scientific evidence that evolution changed anything. It is all 100% postulation. What instead we are looking at is how God created us. Amazingly different than the animals. And all for a purpose.

True science is a study of and a trying to understand this creation.



Gee that's a great way to say that you are profoundly ignorant regarding science, and intend to stay that way, because that is the only way you can feel good about saying utterly idiotic things regarding science or evolution.

Now that you're done defining what "true science" is, no doubt you are going to define "true math" which will make it easy to explain that the world is not billions of years old. Then you are going to define what a "fact" is and that will be anything you believe to be true regardless of whether or not it is.
LariAnn
1.8 / 5 (5) Feb 18, 2013
Biology and its observed basic process of population change is a science accepted by all scientists. And of course we _can't_ study ideas ("creation"!?) that we know from observation hasn't happened.


If by "creation", you refer to "creation by God (or gods)", then you are correct in stating that we have not observed it happening. We also have not observed a lot of things taken as fact in evolutionary theory, but which are actually beliefs on the part of those who advocate them.

If by "creation", you mean "creation driven by intelligence", then you are completely wrong in your assertion because creation driven by intelligence is quite common and observable today. To assert that it hasn't been observed, you'd have to demonstrate how the computer you used to post your comment (and the internet that allows such postings) came into existence without any intelligent design.
RealScience
5 / 5 (3) Feb 19, 2013
... is the only model for adaptive evolution. The fact that random mutations are excluded as cause threatens non-believers


@JVK - The facts are that mutations happen, and that natural selection selects for some mutations (such as the sickle cell mutations) as part of adaptive evolution. You have failed in other threads to refute these facts, and no matter how much you stick your head in the sand and ignore mutations, evolution will continue using them.
JVK
1 / 5 (4) Feb 19, 2013
Unfortunately, there is no evidence that adaptive evolution has ever used random mutations. Even the latest information on an alanine substitution for valine links one nutrient-dependent change to the epigenetic tweaking of immense gene networks via thermoregulation of intermolecular interactions and protein synthesis with downstream effects on phenotypic traits in a human population that can be selected via the metabolism of the nutrients to pheromones. Thus, we are stuck with your nonsense about the fact that I cannot prove what doesn't occur due to random mutations at the same time there is more scientific substantiation for nutrient-dependent pheromone-controlled adaptive evolution from microbes to man (e.g., because the molecular mechanisms of thermoregulation extend from what occurs with non-random DNA strand pairing in microbes to the mouse model of human thermoregulation via eccrine sweat and apocrine gland secretion of pheromone precursors). You're not very bright, are you?
RealScience
5 / 5 (4) Feb 19, 2013
Unfortunately, there is no evidence that adaptive evolution has ever used random mutations.

While individual mutations are unpredictable, mutations as a whole are far from random. Life has evolved to evolve, including having fewer mutations initially, and to more diligently repair mutations, in areas where mutations are usually fatal. Mutations also occur more often in DNA that is in use than in DNA that is tightly packed, and also to occur more often in repetitious segments (e.g., copy number variations).

That being said, you have still FAILED to refute the example of sickle cell mutations being selected for, which is a counter example to your statement. And when you use "no evidence ... ever", a single counter example proves your statement wrong.

JVK
1 / 5 (5) Feb 19, 2013
"the example of sickle cell mutations being selected for" is the most ridiculous pertubation of biological facts ever proposed. Take something only exhibited at the population level in humans and claim that a mutation somehow caused it. This, when the molecular mechanisms of nutrient-dependent pheromone-controlled adaptive evolution are perfectly clear and need only the substitution of one amino acid in a base pair that epigenetically tweaks cellular differentiation in cells and in tissues of adaptively evolved organisms. All animal models tell us that this is how adaptive evolution occurs. No animal model shows that mutations are adaptive. What some people call adaptive mutations or variants that lead to adaptations are nutrient-dependent (i.e., by Natural Selection) and pheromone-controlled (i.e., by reproduction). See for example: http://phys.org/n...tml#nwlt The substitution is nutrient-dependent and its result is pheromone-controlled reproduction.
RealScience
5 / 5 (4) Feb 19, 2013
"the example of sickle cell mutations being selected for" is the most ridiculous pertubation of biological facts ever proposed. Take something only exhibited at the population level in humans and claim that a mutation somehow caused it.

There are five different sickle-cell mutations already known to persist in malaria-prone regions. This is not a model - this is reality.

No one in this thread has said that nutrients and pheromones aren't involved in evolution. Your own reference shows that pheromone variety can be increased by mutation:
"Our results show that a single mutation, which leads to the substitution of a critical amino acid, is sufficient to create a new pheromone blend".
Since mutations can alter a pheromone blend and are inherited, natural selection will operate on them. If the blend better attract mates it will be selected for, if worse it will be selected against.
JVK
1 / 5 (4) Feb 19, 2013
Nutrient-driven changes in intracellular signaling and stochastic gene expression that result in selection for phenotypic characteristics are not due to mutations. Substitution of an amino acid cannot occur unless it is there to be substituted. What they convey to people like you is merely the only representation you can accept while you continue to cling to a ridiculous theory -- never attempting to learn any biological facts.
jsdarkdestruction
5 / 5 (4) Feb 20, 2013
"It is all 100% postulation. What instead we are looking at is how God created us."
the hypocritical nature of that statement is mind boggling. it is the exact opposite, your creation by a magical being is total 100% postulation on your part and evolution is very very well supported by all the actual evidence we have seen all around us.
RealScience
5 / 5 (3) Feb 20, 2013
Substitution of an amino acid cannot occur unless it is there to be substituted.

Mutations can add amino acids or remove them. The most common is in changing the number of repeats in a repeated sequence, but longer sequences also get repeated and deleted, and single bases also occasionally get deleted.
Even entire genes can get extra copies added, although such major changes are typically harmful.
Finally entire genomes occasionally get duplicated, providing plenty of extra genes for mutations to act on.