Humans stop evolving?

[Pyrotex]

Interesting thread. Interesting points of view. Interesting comments.

 

My only contribution here is to tactfully suggest that "we" may be confusing or conjoining two distinct processes here. They are:

Evolutionary change, and

Evolutionary pressure.

 

Several folks have declared that for Humans, "evolution has stopped". I suggest that what they are referring to is "evolutionary pressure". Certainly, with our medicines and wheelchairs and operations and disinfectants, we have reduced the "evolutionary pressure" on ourselves to near zero. In some countries and regions, at least.

 

But "evolution" itself must go on by the very nature of our procreative process. If I am procreated with half my genes from my mother and half from my father, then I am a product of evolution. I am a datapoint in a long process of evolution. Even if there is almost no "evolutionary pressure" on me.

 

I may be short, ugly, weak, have warts, seizures and green skin. But in today's society, as long as my life expectancy is at least 18 years, I have as good a chance as any guy of finding a scantily dressed fertile woman under the influence of alchohol in the back seat of my car. Bingo! My genes get passed on!

 

What my erstwhile progeny does with those genes is their problem.

 

Some folks may be confusing "evolution" with "evolutionary change". When evolutionary pressure is low, survivability of all (viable) genes is more or less assured, leading to a great deal of population diversity. Well, isn't an increase in diversity part of "evolution"? I would think so. "Evolutionary change" is any change, not just change in a particular direction. A change in diversity would still count as "evolution" even if the average change was zero.

 

I still think that the very nature of sexual reproduction makes evolution inevitable. Almost by definition. What we are seeing is that evolutionary pressure on Humans is currently at a very low value, and therefore the evolutionary change that we see is manifested only as increased diversity. So be it. That's still evolution.

 

And when the oil runs out, and the fish run out, and lights go out, and evolutionary pressure suddenly shoots off scale ...

 

... well, then we will see the other side of the evolutionary coin.

[Michaelangelica]

Good points Boerseun,

I am not even sure 'evolutionary pressure' has stopped.

Our bodies now need to learn how

to cope with all the thousands of persistent, man made chemicals in our environment.

How to cope with a sedentary lifestyle in front of a computer screen.

How to cope with a diet rich in refined sugars and carbohydrate and lipids.

How to cope with a density of human population never before seen on earth.

How to cope with the greatest loss in biodiversity since the dinosaurs died.

 

As our environment changes, our challenges change, soon we will need to re-learn how to breathe underwater again.:)

[Eclogite]

The thing is, amongst humans, the next generation is clearly not determined by the environment any more..

But it is. The change in the environment - medical technology, improved diets, etc - has altered what genes can be accepted as fit. The change in the genetic character of the population is largely due to the change in the environment. this is the exact opposite of what you are incorrectly asserting.

 

We have no idea how it would pan out, but it clearly is not evolution in the classical sense.

It is precisely evolution in the classic sense: organisms responding to their environment. you claim the human impact on the environment is large and unique. I grant you it is quantitatively unusual, but certainly not unique. A flock of locusts has a dramatic impact on its environment. Predator species numbers rise and fall with their prey. Their prey numbers are determined to a great extent by the success or failure of the predators. The environment was created by the participants in the environment. It has always been that way and will continue that way as long as life exists.

 

There is no selection taking place anymore..

Yes there is. It a selection that has relaxed somewhat in some directions (and tightened in others), but there is still selection. I see many parallels with the outburst of new forms that occur after an extinction event. There is reduced competition in such a setting so that less tham 'optimum' gene pools can develop and prosper. Some of the genes you consider non-viable (which they clearly are not since their 'owners' survive in this new environment) may lead to major advances in some future generation.

 

- oh well, I should probably not post while inebriated..

True. That is an evolutionary blind alley. the best plan is to have another drink.

[Ben]

But it is. The change in the environment - medical technology, improved diets, etc - has altered what genes can be accepted as fit. The change in the genetic character of the population is largely due to the change in the environment.

While I largely agree with you, Eclogigte, I think you are being slightly fast-and-loose with terminology. So, for example, "change in the genetic character of the population" does not, it the strictest sense, mean very much. The classical definition of evolution is a change, over time, of allele frequencies in a population. With that proviso, I agree

 

It is precisely evolution in the classic sense: organisms responding to their environment.

Likewise - organisms do NOT respond to their environment, populations do, over evolutionary time via random mutation and selection. This gives rise to speciation, again over evolutionary time

you claim the human impact on the environment is large and unique. I grant you it is quantitatively unusual, but certainly not unique. [A flock of locusts has a dramatic impact on its environment.

Yeah but we are talking GLOBAL here, there is a difference. Consider the extinction of the dinosaurs. It is postulated (rightly or wrongly I cannot say) that this was precipitated by a massive meteor strike in Siberia that altered Earth's atmosphere in a way that was incompatible with their lifestyle world-wide, so to speak

 

Predator species numbers rise and fall with their prey.

Yeah, and this is obviously cyclical in a way that Man's effect on his own environment is extremely unlikely to be. Moreover, the rise and fall of predator and prey species has NOTHING to do with evolution - it is simply population fluctuation

Some of the genes you consider non-viable (which they clearly are not since their 'owners' survive in this new environment) may lead to major advances in some future generation.

I have no idea what this means. What is a "non-viable gene"? What is an "advance" in evolutionary terms?

[alexander]

Sorry to jump in, kind of late, and i honestly read only a hand full of the responses.

 

I strongly disagree with the statement in the title, what exactly would constitute the stop or pause of evolution of humans, we constantly adapt, and evolve... Sure if you look at a big picture, we are not all growing spikes and 3rd legs, but nothing stops evolution as a process. For example, change in our ways of living has changed us to be generally taller then humans some 500 years ago. Another more recent evolutionary change, our limbic system, for example, what has become of our flight response? In today's urban environment running away from whatever it is that is threatening us is no longer an option, at least an easy one, so we have learned and genetically programmed ourselves to respond in other ways. Distance physically, for example if you are disagreeing with someone you might not run away, but you might lean away from each, lean back in your chair and move it slightly away from the table, women can put their purse on their lap, or turn away, usually also pointing their feet away, often in the direction of the nearest exit, distance psychologically, put your hands on your face, or rub your eyes, these are all limbic flight responses that we have evolved to suit our modern environment, these are hard wired in our mammal brain. And it is something that is completely, vastly different then what we would see some 4-5000 years ago, pretty different from 1000 years ago, and different enough from just 150 years ago...

[geneyoonit]

wooa first post after joining this forum! (yaaay? :artgallery:)

 

i also only read a handful of responses and must agree with the general consensus that humans are still evolving, in the "simplest" molecular level as well as the overall "long-term" evolution as well...

 

it definitely is an intriguing question though (the reason why i read this thread in the first place), because this question can lead to possibly hypothesizing exactly what the next step for homo sapiens will be, or even giving rise to other questions such as when homo sapiens will no longer be "considered" homo sapiens any longer (due to genetic differences, being unable to reproduce with said homo sapiens, or all the other biological characteristics in telling species apart)...

[Michaelangelica]

Still seems to be a lot of Nazi and racist and protestant and confused thinking surrounding the Law of Natural Selection.

Thanks for helping to clear it up.

[alexander]

no doubt, people have always adapted 1/2 way decent ideas in weird ways to benefit their beliefs, Michael, needn't look farther then the development of theology to confirm that people have done it for a while...

[Ben]

So, I confess I haven't this thread in its entirety, but I am slightly confused by Alexander's and Michaelangelica's recent posts.

 

If you don't like the geneticist's definition of evolution - change in allele frequency over time - consider this.

 

Evolution has no "direction"; that is, the only "betterment" of an evolving species is to be better adapted to the environment in which it finds itself AND that this is heritable; I insist on this qualification.

 

Assume for argument a stable environment and some species perfectly adapted to it. Now let that environment suddenly change. Then either this species becomes extinct, or variant genes appear (or are revealed) that allow a sub-population to survive its changed environment.

 

It would be folly to argue that any change in environment would automatically mean this sub-population - and emerging new species - is "superior" in any absolute sense to its precursors, since "superiority" is relative to a particular ecological niche.

 

In fact, it is easy to imagine changes to our own environment - climatic or nuclear catastrophe, say - where the things we pride ourselves on as being "higher", like exquisite manual and mental dexterity, are of no survival value whatever, and that the best survival strategy, in evolutionary terms, is a heritable return to a Neanderthal-like state.

 

In its own way, this would be an "advance" in survival terms; whether such beings would be in any absolutist sense "superior" is a matter for philosophers, not scientists.

[alexander]

what about my post confuses you, Ben? I never said anything about disagreeing with either genetics definition of evolution nor with evolution itself... so what is confusing you?

[philiplaos]

I think the last time humans made an evolutionary significant change was in 1918. In that year a large proportion of the human population (30%-40%?) died from a worldwide flu pandemic. Presumably, the people who died were more susceptible individuals and those who survived had higher levels of resistance to that partcular flu strain. Through subsequent reproduction, those resistance charecteristics should now be widespread throughout the global population.

 

But maybe that's wrong!:(:(

[Illiad]

We still work our brains. We could become extremely smart wimps.

[Ben]

what about my post confuses you, Ben?

Just this, and no offense intended

For example, change in our ways of living has changed us to be generally taller then humans some 500 years ago.

This is easily explained by dietary changes; what would be the selection pressure that caused we humans to be taller over evolutionary time? In fact you answered my question yourself - change in our way of living is just that; it's not evolution

we have learned and genetically programmed ourselves to respond in other ways.

Sorry, but this is a complete non-sequitur. We can learn, for sure, but we cannot "genetically programme ourselves". How on Earth would we do this? Like "thoughts alter DNA", for example? Please,.

these are all limbic flight responses that we have evolved to suit our modern environment,

Well first off, WE haven't evolved anything - evolution just happens

these are hard wired in our mammal brain. And it is something that is completely, vastly different then what we would see some 4-5000 years ago, pretty different from 1000 years ago, and different enough from just 150 years ago...

Sorry, but there is a serious misunderstanding here. If something is "hard wired", then the paradigm says (rightly or wrongly) that there are alleles responsible for this hard wiring that have been selected for. What explicit form this takes is cultural, environmental, learned.

 

So changes in this explicit form is not evolution in the sense that biologists use the term.

[Eclogite]

Sorry, but there is a serious misunderstanding here. If something is "hard wired", then the paradigm says (rightly or wrongly) that there are alleles responsible for this hard wiring that have been selected for. What explicit form this takes is cultural, environmental, learned..

I think you have misread alexander. He says that the flight response is hardwired. The expression of that response is cultrually determined. If he is not saying that then he is wrong on that point.

[Ben]

I think you have misread alexander. He says that the flight response is hardwired. The expression of that response is cultrually determined. If he is not saying that then he is wrong on that point.

Well, judge for yourself

Another more recent evolutionary change, our limbic system, we have learned and genetically programmed ourselves to respond in other ways.

If I misinterpreted this, I apologize. But I cannot see any other way to read it

[Michaelangelica]

Human diet is so diverse, I think that we're just getting an initial glimpse of what's likely to be really huge area of variation that differentiates populations of humans."

 

The human digestive tract harbors trillions of bacteria, many of which establish lifetime, symbiotic relationships with their hosts.

The food we eat nourishes our gut flora, and those bacteria feed us with the products and byproducts of their own digestive activities.

 

Consequently, the gut microbiome has evolved to encode a variety of digestive enzymes, for example, those that break down hard-to-digest polysaccharides in food plants, such as celery, broccoli, and other vegetables.

 

. . .

 

Mining the databases for other marine bacteria that might also contain these so-called porphyranases,

. . .gut microbe had somehow obtained those genes directly from the marine species. "I was really blown away by this result," he recalled.

 

Japanese people regularly consume sushi wrapped in seaweed, which carries with it marine bacteria that produce porphyranases. "It was directly obvious for us that this was horizontal gene transfer from the ocean to the Japanese gut," Hehemann said. "As far as I know, there has not before been an example of horizontal gene transfer between different ecosystems."

 

. . .

Removing many harmful bacteria from foods has dramatically reduced food-borne diseases in recent decades, he said, "but I think there's a likely cost -- the loss of microbes that are not harmful." Such microbes may transfer seemingly beneficial genes to the gut biome, increasing its ability to adapt to changes in diet, as well as fine-tune the immune system, such that "if you begin to eradicate microbes with which we have coevolved, that has the potential [to disrupt] homeostasis," Sonnenburg said.

 

Read more: Gut bacteria are what we eat - The Scientist - Magazine of the Life Sciences Gut bacteria are what we eat - The Scientist - Magazine of the Life Sciences

 

Read more: Gut bacteria are what we eat - The Scientist - Magazine of the Life Sciences Gut bacteria are what we eat - The Scientist - Magazine of the Life Sciences

Gut bacteria are what we eat - The Scientist - Magazine of the Life Sciences

[hummingbird]

according to drawin's theory. evolution is caused by natural selection which adaptable ones survive and reproduce.

 

but in today's society, things change... ppl having bad traits (like some sickness....whatever) will not die off, we have hospital, and they can have a love one and have some children. also, ppl having good trait wont reproduce a lot of offsprings, because we are educated ppl. that means natural selection is stopped?

 

 

Well I was wondering if there are signs of evolution and even started a post on indigo children actually just being part of our evolution. So I guess I'm going to push for there being a evolving taking place. We evolve to better handle the ways were pushing for, and if thats tech way than most likely thats what we will see.