“Backward evolution” spawns ape-like people

[Dardedar]

DAR
At first I thought this may be an April fools joke, but we are a little early for that. Facinating:

****
“Backward evolution” spawns ape-like people

Feb. 21, 2006
Special to World Science

An editor of a noted scientific journal says he has discovered a genetic defect that seems to set back the clock on human evolution by more than a million years.

Its victims walk on all fours and mouth a primitive language, the scientist reported. He added that the syndrome may literally undo eons of evolution, and thus reflect with some accuracy what our ape-like ancestors were like.

The researcher, Uner Tan of Cukurova University Medical School in Adana, Turkey, has posted an online video clip of an affected woman walking on all fours, her face blurred.

The idea that evolution can run backward isn’t new; some scientists say there have been confirmed cases of it in animals. But it’s also a controversial subject, and considered hard to prove in any given case.

Walking patterns of victims of Uner Tan syndrome. (Courtesy Uner Tan/ International Journal of Neuroscience)
Tan, at any rate, argued that this could be a case of it, so the mutation—known to run in one Turkish family—might offer scientists an unprecedented glimpse into human origins.

“This syndrome interestingly exhibits prehuman features” and represents “possible backward evolution,” he wrote in a paper describing the condition. As such, it “can be considered a live model for human evolution.”

The paper appears in the March issue of the International Journal of Neuroscience, where Tan sits on the editorial board. He also named the condition after himself: Unertan syndrome.

...

The rest is here:

http://www.world-science.net/exclusives ... tanfrm.htm

[Savonarola]

Here is the thread on iidb that discusses this. There are some good points, some of which I will succinctly reproduce here.

The term "backward evolution" is a bit misleading in that it can be misconstrued to suggest that evolution has an inherent direction. This is quite obviously not the case. We can probably expect uneducated journalists continuing to present this poorly.

The claims that the genetic change "sets back the clock on human evolution" is disingenuous at best. The syndrome includes mental retardation, incomplete brain development, and loss of motor control. There is no mention of pelvic abnormality, spine/pelvis interface abnormality, or spine/skull interface abnormality. This seriously conflicts with the position that this genetic trait is a window into the quadraped locomotion of the past (especially as our ancestors were knuckle-walkers and not palm-walkers).

This looks a lot more like a developmental problem of the central nervous system, not a reversion to an earlier form.

[Doug]

DAR
At first I thought this may be an April fools joke, but we are a little early for that. Facinating:

DOUG
I think it's a hoax.

[Dardedar]

The term "backward evolution" is a bit misleading in that it can be misconstrued to suggest that evolution has an inherent direction. This is quite obviously not the case. We can probably expect uneducated journalists continuing to present this poorly.

DAR
From the top link at this same site:

"Scientific doubts on reverse evolution, Crandall wrote, have nothing to do with a popular misconception that evolution “has no direction.” It does to some extent, he argued—species tend to become better suited to their environment—and that may be irrelevant anyway, since a return to an ancestral state can occur whether or not one thinks of evolution as directed.

“I don’t know of any evolutionary biologists who would subscribe to the notion that reverse evolution is impossible,” Crandall wrote. “It doesn’t take long in evolutionary biology to figure out that nothing is impossible!”

DAR
All they have is this Brigham Young guy and someone else from Portugal talking about it. I need to see something about this from some site other than just this one before I'll take it too seriously.

D.

[Savonarola]

Reverse evolution occurs when an organism returns to the genetic state of its ancestors, said Crandall, who wrote a paper on the topic in the Oct. 2003 issue of the research journal Trends in Ecology and Evolution. In that work, he wrote that reverse evolution is documented in various organisms, such as fish that lose their eyes after living in dark caves for generations.

The Turkish researcher, Uner Tan of Cukurova University Medical School in Adana, Turkey, argued that something similar may have afflicted the family in Turkey: a mutation stripped them of the genes or genes that let humans walk upright, returning them to the pre-human state of quadrupedalism, or four-limbed walking.

Man, once again, I have to say that I hate going against people with higher qualifications than mine... But yeesh.
In my opinion, a better explanation of the cave fish blindness example is "evolution that has taken a morphologic u-turn," not "reversal." I am doubtful that the very same genetic changes that produced the ability to see in cave fish were precisely undone after many generations in the dark. Rather, any genetic change that resulted in blindness would be neutral and therefore not selected against, not just whichever changes produced vision in the first place.

If someone were born with a genetic condition that prevents him or her from being able to see, for example, do we consider that reverse evolution? Of course not. We need not ignore that these siblings have deficiencies in brain function and below average motor control, according to the abstract. This isn't a perfect analogy, but: infants can't walk because they lack, at the very least, appropriate motor control and experiential knowledge of things like balance and leverage. I'll have to admit that my knowledge of research into bipedalism isn't the least bit impressive, but if this 17p gene seems to cause lessened brain function and ataxia, I can't say I'm convinced. Perhaps more research will be available in the near future.

Additionally, seven people were affected, according to the abstract, but only five never learned to walk on two legs. I could presumably explain this from my point of view by saying that perhaps the two walkers were able to learn how to walk despite their ataxia. If this genetic defect were actually ridding them of the ability to walk upright, as Tan suspects, what is his viewpoint regarding these other two?

[Doug]

In my opinion, a better explanation of the cave fish blindness example is "evolution that has taken a morphologic u-turn," not "reversal." I am doubtful that the very same genetic changes that produced the ability to see in cave fish were precisely undone after many generations in the dark. Rather, any genetic change that resulted in blindness would be neutral and therefore not selected against, not just whichever changes produced vision in the first place.

DOUG
I agree. It is not even clear what it would mean to say that evolution has been "reversed." It is just more evolution.

Perhaps fish who evolved eyes and then find themselves no longer in need of them would have the eyes selected out to save energy, i.e. the fish whose eyes ceased using so much of their food energy would have an advantage over those who still had functioning eyes. That's just evolution, not "reversal."

[Barbara Fitzpatrick]

There are quite a number of species that have gone through the "morphologic u-turn" over the course of the several billion years there has been life on this planet. Whales, for example, were once quadripedial land animals, and snakes once had legs. Evolution basically means physical or mental adaptations that make the species more prone to survival are made/kept, but neutral traits aren't discarded. Human body still includes an appendix. For reasons we don't understand, blind cavefish had a survival advantage over sighted cavefish - and it didn't happen in 1 generation. If the whole situation in the article isn't a hoax, we're looking at a case of genetic damage, not evolution.

[Savonarola]

... but neutral traits aren't discarded.

Just to clarify for any readers, neutral traits aren't discarded with prejudice, anyway. Genetic drift, which is an effect of random genetic sampling (i.e. breeding), can eliminate neutral traits from a population, however.

For reasons we don't understand, blind cavefish had a survival advantage over sighted cavefish

Do you have a source for that, Barbara? I could be mistaken, but it was my understanding that the cavefishes' eyesight simply was not conserved because there was no selective "reason" to conserve it in dark caves. This would mean that blind cavefish had no fitness difference from seeing fish. Genetic drift takes over from there.
One could make the argument that lacking the eye increased fitness, as it certainly causes damage to get poked firmly in the eye or get eye infections, but there need not be any fitness advantage of blindness for blindness to become prevalent.

[Barbara Fitzpatrick]

Can't cite chapter and verse, but it's in one of the later books by Elaine Morgan dealing with the Aquatic Ape Hypothesis. Also extrapolated from various scientific articles finding evolutionary advantage to traits previously thought neutral, if not detrimental - sickle cell anemia genes providing protection from malaria, for example, and the increased absorption of vit D from UV rays of "white" skin. There are tentative links between type A blood and consumption of grain, type B blood and consumption of dairy products (just starting through the testing/peer review stage), ditto eye color and ability to deal with glare - many things we used to attribute to genetic drift are now being investigated as having positive survival correlations to the environment they are suggested to have developed in. However, aside from the Elaine Morgan books, they are basically articles I read in the science section of NYT or Reuters - just thought, "how interesting" and moved on.