Humans Evolving Faster Than Ever

Kwyj1b0 writes "In a massive study on genetic variation among humans, researchers found that most changes have occurred in the last 200 generations, too fast for natural selection to catch up. Recent papers show that rare genetic variations have a more drastic effect than previously believed. Another result shows that 'we carry a much larger load of deleterious variants' (as well as positive variants) than our ancestors 200 generations ago."

Comments

This this not evolution

[Ubi_NL]

Acquisition of mutations is not evolution. Evolution is the combination of variations AND selection of those traits that increase fitness. The fact that we only acquire more genetic mutations means that selectionhas gone down and evolution with it. The simple explanation is that healt care enabled us to cheat on selection.

Re:This this not evolution

[Fallingcow]

What does "help" mean, in an evolutionary context?

Seems to me that culture is just another factor to which an organism may, over generations, adapt.

Re:This this not evolution

[binarstu]

The parent is simply wrong. Acquisition of mutations most certainly is evolution, and evolution does not require natural selection.

Natural selection is one mechanism of evolution, but not the only one, and evolution does not have to increase fitness. Ever since the "modern evolutionary synthesis," evolution is often defined as the change of allele frequencies in a population over time. Such change might be due to natural selection, or it might be due to other non-selective forces, such as genetic drift. To say that again, natural selection is not required for evolution. Introduction of new alleles due to mutations, random fixation or loss of alleles due to genetic drift, changes in allele frequencies due to population bottleneck events, and so on, all can cause evolution without natural selection.

Wikipedia has more information about natural selection and non-selective factors contributing to evolutionary change.

Re:This this not evolution

[Arancaytar]

Wrong.

Humans are still reproducing, surviving and dying. Traits are still selected. They're just different traits than the ones that would have been selected if humanity were still living in caves. The fitness function has been loosened, and the net is cast wider now - instead of mutations having to benefit (or not adversely affect) the immediate survival of the individual, there is more room for variety.

A species with a secured infrastructure can afford to gamble on outliers, who would not have survived prior to modern technology. Those gambles can pay off big-time. The absence of an outdated pre-civilization fitness function killing everyone with motor paralysis is what allows our species to benefit from a genius with motor paralysis.

Re:This this not evolution

[Qbertino]

What health care was there 200 generations ago?

Pretty good healthcare in some parts of the world. Arabia and parts of the Byzantine Era, for instance, were a high culture more than a thousand years ago with complete health care coverage and other public services. Including stuff you'd have considered high-tech right up to magical in other parts of the world. Water clocks, aquaeducts, mechanical devices, sophisticated smithery and metal working, a school system, superiour math, accounting and efficiency measurement techniques, etc. As for the public healthcare, there are written acounts of people being thrown out of hospitals because they were still enjoying the pampering even though they were well again.

Which, on a sidenote, goes to show how things go down the drain once religious fanatics take over.

Re:This this not evolution

[Kjella]

So is fabrication of fire arms, but both are not evolution in theway we have defined the term evolution.

Well you're right in that if we saw people with machine guns slaughter guys with muskets, we wouldn't call that evolution. Neither is going from 6-7 children/woman to 2-3 children/woman as many countries have done in a generation or two. It's only evolution if there's a reasonably clear link between your genetic makeup and your ability/probability to reproduce. I don't see much chance that a random mutation would help me survive a bullet, though there's a good chance that personality traits that are genetic could help me avoid a situation (or worse, put me in a situation) where I get shot. That's real evolutionary pressure right there, though I think the number of people shot and killed is too small to have any real significance.

But in terms of culture then genetics is a huge part of attractiveness, including appearance, personality and intelligence. That can have both direct effects to hooking up and indirect effects like social circle, social status and economic status. And perhaps even far more so today, how many kids you want to have. Sure society is a huge influence here but ultimately it comes down to personal choice that may be a lot more built in than people realize. Changing culture also makes different genes important, in a society with pre-arranged marriages your courtship genes might not matter much but in a society of free selection they do. That is a new selection pressure right there.

Re:This this not evolution

[RabidReindeer]

I should add that selection based on culture (love, pre-arranged weddings etc) rather than fitness also does not help evolution.

Your definition of "fitness" is not the Darwinian definition. It sounds, in fact, more like the pseudo-Darwinian conceit that "fitness" means the ability to kill or resist being killed. When Darwin said "survival", he didn't mean "last person on the island", he meant that the species in question had found a niche where its population would be stable.

Survivability comes in many forms. Some, like tigers are primarily solitary. Some, like herd animals, depend on the group. We have ample evidence these days that in many cases, survivability (in the Darwinian sense), can come even from relatives who never directly contribute DNA to the continuation of the species.

Love as a primarily positive evolutionary trait can be debated, although certainly being unlovable isn't going to afford many non-violent ways to swim in the gene pool. Pre-arranged weddings, on the other hand, can make the difference between a tribe being exterminated or being able to ally itself with other tribes. Systems of laws and mores can ensure that the unlovable whose sole means of propagation is rape will be taken out of circulation relatively quickly.

Social structures as evolutionary forces are not unique to the human race. But they are a powerful contributor. If we went strictly on kill or be killed based on physical fitness, we probably wouldn't have produced a Stephen Hawking.

Re:This this not evolution

[devleopard]

Software engineering does not introduce random mutations into the Software

You obviously haven't worked with some of the developers I've worked with

Re:It's "Survival of the Fit-enough"...

[flonker]

The frightening aspect of this is that population may expand its genetic diversity to fill the 'fit enough" gene pool. Then it will overflow the "fit enough" gene pool by creating mutations that can't survive even with health care, bringing survival back down, albeit with increased genetic variety such that many can't survive without constant medical treatment.

That is to say, we will evolve to require medical treatment.

Times of plenty

[chrisjbuck]

I think population dynamics show that in times of plenty (little natural selection, abundant food) populations explode, what the human population has been doing the last 100+ years. It's the spring that doesn't come or massive outbreak of disease or new dominant predator that culls the population, when that selection occurs the random genetic variations may give rise to competitive advantages. It is only after the population goes through the selection event that any mutations that proved advantageous will spread right through the population, then the population has evolved. Before the selection event the population is just randomly diverging.

True!

[rew]

Absolutely true!

Evolution works that way: In good times, a big population is generated that has great genetic variety. When bad times come along, the bad genetic variations will be removed from the population.

Suppose for instance that suddenly tomorrow all oaktrees had pollen that is deadly to most humans. The genetic variations builtup over the last 200 years might have provided a (possibly small) percentage of the population that is resistant to the deadly pollen. The result would be that a small group survives and starts working on a new gene-pool.

Yes, genetically we have been living in "good times" the last generations. More and more "slight defects" in the genetic pool are able to survive into mature ages.

A friend is totally colorblind. A genetic disadvantage, you'd say? Nope, his "grayvision" is a LOT better than that of most of us. Apparently he can spot camouflaged army-material from way further away than us normal people. When suddenly THAT becomes a winning trait (i.e. those that don't have it die), his descendants will form a larger part of the population.

This expansion of the gene pool also allows for combinations. Suppose the guy with the super-vision marries the gal with the super hearing?

Re:You don't supppose, do you...

[Hognoxious]

200 generations, not 200 years. The difference is a factor of 20 or so.

It's left as an exercise for the reader to make a joke about Pakistan, Utah or Rotherham.

Summary shows poor understanding of evolution

[SpinyNorman]

In a massive study on genetic variation among humans, researchers found that most changes have occurred in the last 200 generations, too fast for natural selection to catch up.

This statement appears to reflect a misunderstanding of how evolution plays out in practice.

The way evolution is often taught is that the small genetic changes in each generation make a difference to the evolutionary fitness (relative to his/her peers) of the individual right away, but that the changes are so small that it takes very many generations to see divergence of sub-populations of the species and hence noticeable evolutionary change.

The reality of evolution - "puntuated equilibrium" - is different from this simplistic teaching model. What really happens is that genetic changes accumulate over very many generations but don't have much if any immediate effect on evolutionary fitness since in practice these small, incremental, personal changes are often not what drives evolution. What really drives evolution (per the inference of the fossil record) is when the *environment* (weather, food supply, disease, competitors, etc, etc) changes, often very quickly, causing accumulated genetic change to suddenly become relevant... what had previously been a benign genetic change (disease resistance or susceptibility, etc, etc) no suddenly becomes a huge change in evolutionary fitness in the new environment, and and the fate of different genetic subpopulations becomes very differnt (we see visible divergence).

This is "punctuated equlibrium" - long spans of no visible evolutionary change (equilibrium) are puntuated by brief spans of rapid visible change as accumulated genetic drift suddenly becomes relevant due to environmental change.

So... the notion of 200 generations being too quick for "natural selection to keep up" is bogus. Natural selection mosltly doesn't happen every generation - it only happens when those infrequent major environmental changes occur.