Human Evolution: Are Humans Still Evolving?

[amicus]

http://news.yahoo.com/s/time/20091024/hl_time/08599193175700



By EBEN HARRELL Eben Harrell – Sat Oct 24, 10:10 am ET

Modern Homo sapiens is still evolving. Despite the long-held view that natural selection has ceased to affect humans because almost everybody now lives long enough to have children, a new study of a contemporary Massachusetts population offers evidence of evolution still in action.

A team of scientists led by Yale University evolutionary biologist Stephen Stearns suggests that if the natural selection of fitter traits is no longer driven by survival, perhaps it owes to differences in women's fertility. "Variations in reproductive success still exist among humans, and therefore some traits related to fertility continue to be shaped by natural selection," Stearns says. That is, women who have more children are more likely to pass on certain traits to their progeny. (See the top 10 scientific discoveries of 2008.)
Stearns' team examined the vital statistics of 2,238 postmenopausal women participating in the Framingham Heart Study, which has tracked the medical histories of some 14,000 residents of Framingham, Mass., since 1948.

Investigators searched for correlations between women's physical characteristics - including height, weight, blood pressure and cholesterol levels - and the number of offspring they produced. According to their findings, it was stout, slightly plump (but not obese) women who tended to have more children - "Women with very low body fat don't ovulate," Stearns explains - as did women with lower blood pressure and cholesterol levels. Using a sophisticated statistical analysis that controlled for any social or cultural factors that could impact childbearing, researchers determined that these characteristics were passed on genetically from mothers to daughters and granddaughters.

If these trends were to continue with no cultural changes in the town for the next 10 generations, by 2409 the average Framingham woman would be 2 cm (0.8 in) shorter, 1 kg (2.2 lb.) heavier, have a healthier heart, have her first child five months earlier and enter menopause 10 months later than a woman today, the study found. "That rate of evolution is slow but pretty similar to what we see in other plants and animals. Humans don't seem to be any exception," Stearns says. (See TIME's photo-essay "Happy 200th Darwin Day.")
Douglas Ewbank, a demographer at the University of Pennsylvania who undertook the statistical analysis for the study, which was published Oct. 21 in the Proceedings of the National Academy of Sciences (PNAS), says that because cultural factors tend to have a much more prominent impact than natural selection in the shaping of future generations, people tend to write off the effect of evolution. "Those changes we predict for 2409 could be wiped out by something as simple as a new school-lunch program. But whatever happens, it's likely that in 2409, Framingham women will be 2 cm shorter and 1 kg heavier than they would have been without natural selection. Evolution is a very slow process. We don't see it if we look at our grandparents, but it's there."

Other recent genetic research has backed up that notion. One study, published in PNAS in 2007 and led by John Hawks, an anthropologist at the University of Wisconsin at Madison, found that some 1,800 human gene variations had become widespread in recent generations because of their modern-day evolutionary benefits. Among those genetic changes, discovered by examining more than 3 million DNA variants in 269 individuals: mutations that allow people to digest milk or resist malaria and others that govern brain development. (Watch TIME's video "Darwin and Lincoln: Birthdays and Evolution.")

But not all evolutionary changes make inherent sense. Since the Industrial Revolution, modern humans have grown taller and stronger, so it's easy to assume that evolution is making humans fitter. But according to anthropologist Peter McAllister, author of Manthropology: the Science of Inadequate Modern Man, the contemporary male has evolved, at least physically, into "the sorriest cohort of masculine Homo sapiens to ever walk the planet." Thanks to genetic differences, an average Neanderthal woman, McAllister notes, could have whupped Arnold Schwarzenegger at his muscular peak in an arm-wrestling match. And prehistoric Australian Aborigines, who typically built up great strength in their joints and muscles through childhood and adolescence, could have easily beat Usain Bolt in a 100-m dash.

Steve Jones, an evolutionary biologist at University College London who has previously held that human evolution was nearing its end, says the Framingham study is indeed an important example of how natural selection still operates through inherited differences in reproductive ability. But Jones argues that variation in female fertility - as measured in the Framingham study - is a much less important factor in human evolution than differences in male fertility. Sperm hold a much higher chance of carrying an error or mutation than an egg, especially among older men. "While it used to be that men had many children in older age to many different women, now men tend to have only a few children at a younger age with one wife. The drop in the number of older fathers has had a major effect on the rate of mutation and has at least reduced the amount of new diversity - the raw material of evolution. Darwin's machine has not stopped, but it surely has slowed greatly," Jones says. (See TIME's special report on the environment.)

Despite evidence that human evolution still functions, biologists concede that it's anyone's guess where it will take us from here. Artificial selection in the form of genetic medicine could push natural selection into obsolescence, but a lethal pandemic or other cataclysm could suddenly make natural selection central to the future of the species. Whatever happens, Jones says, it is worth remembering that Darwin's beautiful theory has suffered a long history of abuse. The bastard science of eugenics, he says, will haunt humanity as long as people are tempted to confuse evolution with improvement. "Uniquely in the living world, what makes humans what we are is in our minds, in our society, and not in our evolution," he says.

~~~~

Not a scholarly piece and all over the place, but questions worth asking in layman's terms for public consumption.

Perhaps you will find it interesting also...

Amicus

 

[amicus]

]I don't think so.[/I]

~~~

A rather paltry response; I suppose you have your reasons?

Amicus

 

[Huckleman2000]

Oddly, I came across this article this morning: Rich 'may evolve into separate species'

The super-rich may evolve into a separate species entirely in the future due to enhancements in biotechnology and robotic engineering, American futurologist Paul Saffo has said.

Mr Saffo, from San Francisco, says in the future people will be able to grow their own replacement organs, take specially tailored drugs, and use genetic research tools to alert them from any possible hereditary health dangers.

He adds that tomorrow's world will be a fusion of biology and technology, where robots do the chores, cars drive themselves and artificial limbs are better than real ones.

Mr Saffo's comments reflect claims by American scientist Ray Kurzweil who only a few months ago said immortality was only 20 years away due to the speed of advancements in nanotechnology.

But Mr Saffo says these improvements would only be affordable to the super-rich. And because of this, he says, advancements may lead to a divide between the classes and eventually could lead to the super-rich evolving into a different species entirely, leaving his not-so-rich counterpart behind.

"In the 1980s it was the personal computer - came out of the garage, changed the world. In the 1990s it was the web. The next big device to wander into our lives is robots,” he told the Sunday Times.

"We may find we are absolutely dependent upon these electronic insects and that we don't even know we are dependent upon them until something breaks.

"I sometimes wonder if the very rich can live, on average, 20 years longer than the poor. That's 20 more years of earning and saving. Think about wealth and power and the advantages that you pass on to your children."

 

[Stella_Omega]

Archaeologists can tell you the date that humans stopped evolving in response to environmental forces; about the time we find tibia bones that were badly broken and were healed, 45,000 years ago. When humans began caring for their wounded, instead of letting them die.

That's the point when humans started to create their own set of evolutionary parameters. We call these human-made forces; culture.

(Interestingly, that's also the date when we begin to see objects that have been made as art as opposed to tools. Which implies that those freakin' bohemian arteest types are crucial to human existance.)

 

[JamesSD]

Of course humans are still evolving. We are, however, held back a bit by our relatively long lives, low total number of offspring, and low infant mortality rates.

It's a difficult issue to talk about in cold, scientific terms, because the forces that shape evolution are the forces that prevent humans from reaching sexual maturity and adulthood. But even in the US and especially worldwide, human children do frequently die of disease and other external factors.

Of course, there's also the "Idiocracy theory" where at least in the US our doctors, lawyers and rocket scientists tend to have few children later in life while Kevin Federline has four kids. While K-Fed may have some evolutionarily advantageous traits, there's a theory that the "unnatural" selection of inability to properly use condoms and birth control may be tilting the human species in a certain direction. However, 2-3 generations is a fairly short time frame in the scope of the evolution of a species. We can start drawing lines and making projections, but it's extremely difficult to predict what society and the world will be like 40 years from now, much less 200.

 

[WRJames]

There is a wonderful Robert Heinlein short story -- Gap -- on the subject of human evolution. It is based on the premise that super smart people will congregate together, in academic settings and the like, and breed even smarter offspring.

This small population after a few generations achieves an IQ a hundred points or more above the norm -- essentially becoming an isolated subspecies.

Of course, this being a Heinlein story, they all think like Ami.

 

[amicus]

I suggest there are far more interesting lines of thought engendered by this piece than has thus far been explored.

Consider one avenue that dawned upon me: nature and all of evolution, the entire history and then just that of man, the only sentient life form that can adapt to environmental changes and more than that, create an artificial environment to suit his needs.

No one 'knows' what the future holds and the implication made by JamesSD, concerning the best and brightest not reproducing at nearly the rate of the lower class, and I add, the minorities of our society in specific, does suggest possible modifications in the near future.

So too, I suggest, does the nearly fifty percent of all children being brought up in single parent families, most of them headed by females. Worthy of at least a little thought, is the possibility that entire generations of children have been, 'feminized', take that as you will, those raised almost exclusively by their mothers, women, women school teachers and women day care providers.

But even that is merely an aside, perhaps dwarfed by the recognition that sophisticated western societies are not a majority of the world's population, and that if the evolution of modern societies differs from that of third world societies, what then?

...interrupted...

amicus

 

[Huckleman2000]

I suggest there are far more interesting lines of thought engendered by this piece than has thus far been explored.[...]
But even that is merely an aside, perhaps dwarfed by the recognition that sophisticated western societies are not a majority of the world's population, and that if the evolution of modern societies differs from that of third world societies, what then?

...interrupted...

amicus

Wow. Seen a light, Ami?

 

[Dragonlipz]

In response to the question posed by Mon Ami:
Progressives certainly are evolving but whether teabaggers are is truly in doubt.....

 

[Liar]

Devolving is just evolving in another direction.

 

[TxRad]

We now have 4th and 5th generation stupid people thanks to OSA and such.