Human evolution as an accelerating process

[Os Cangaceiros]

I was wondering what everyone thought about this:

http://blog.wired.com/wiredscience/2007/12/humans-evolving.html

http://www.physorg.com/news116529402.html

Forgive me if this has been posted before.

[AGITprop]

I don't necessarily believe this. I don't think we are evolving much more if at all. I think these differences perceived in modern humans compared to those of humans 5000 years ago is mainly due changes in diet which has allowed us to grow taller and live longer. Most importantly are our developments through science. Because humans are conscious we can manipulate our environment and require now, practically no physical or genetic change to adapt. For these reasons, I don't see how we can possibly be still evolving as the need for us to do so has disappeared.

[ÑóẊîöʼn]

I don't necessarily believe this. I don't think we are evolving much more if at all.

This study indicates otherwise.


I think these differences perceived in modern humans compared to those of humans 5000 years ago is mainly due changes in diet which has allowed us to grow taller and live longer.

The change in diet doesn't account for the other changes, such as the ability to process simple carbohydrates.


Most importantly are our developments through science. Because humans are conscious we can manipulate our environment and require now, practically no physical or genetic change to adapt. For these reasons, I don't see how we can possibly be still evolving as the need for us to do so has disappeared.

Selection pressures are still existant, they have simply changed. It's just that with increasing control over our bodies and our environment, selection pressures no longer come from those areas.

We are still evolving.

[Devrim]

Doesn't the size of the gene pool tend to reduce the speed of evolution? I am pretty sure that that must be the case.


For these reasons, I don't see how we can possibly be still evolving as the need for us to do so has disappeared.

This sentence shows a very confused view of evolution.

Devrim

[Hegemonicretribution]

As far as I can understand it a situation where some form of evolutionary description wouldn't hold would require no death or birth. Or more generally stability or instability, or existence or non-existence. Forsaking this it will always be sensible to appeal to circumstances (these can be environmental, social, economic etc) in order to explain trends. If not, you explain them as completely chaotic, or ordered by something over and above....

To me the idea that the world is as it is because things have made it how it is is intuitive. To construe those things that give us our current situation as something other than the pressures exerted upon us by our environment (in the broadest sense) seems to me fallacious. This appears very close to something magical, mystical and/or religious and as such is completely unsupported.

The idea that everything is completely chaotic is fair enough, but this is simply a refusal to explain 'what is.' If this is your view, then I don't think there is even a possible way to persuade you otherwise. You choose your paradigm and stick with it, I know which one seems more useful to me (if nothing else). I like explanations, at least to help generate better ones, if not to furnish me with the understanding I need to function.

Anyway it seems that the evolutionary approach holds.

Or the chaotic one if you aren't playing at science.

Or the 'Other' cause of order....choose the one you want, they are all baselss.

Any viable form of the latter two can be better explained in terms of the first. The remaining forms are untenable. Every single thing, fact, state of affairs or anything can be accounted for by evolution, it is just that sometimes the answers aren't as full. What exists exists because it can, what doesn't exist is not here for us to speculate about. There is no exception to this rule, and this is evolutionary theory at its most fundamental. To claim that this no longer applies to humans just seems wrong because I don't believe in impossible humans; those that couldn't exist but can.

Anyway apologies if the tone was a little off here, I am just trying out a new style :thumbup1: I will be less dogmatic again from now on....but you get the point.

[mikelepore]

Evolution selects factors that affect the probability of transmitting one's genes to future generations. Industrial society has made some factors unimportant, for example, we no longer have a significantly greater chance of surviving to reproductive age if we can run faster than a lion or have good eyes to see a crocodile. However, evolution can still select immunity to childhood diseases, resistance to infertility, features considered attractive by the opposite sex, etc.

[DesertShark]

Neither of those articles explain why Africans are the most genetically diverse of all human populations. Also, they talk about a disconnect in gene flow which was true before imperialism and airplanes.


Evolution selects factors that affect the probability of transmitting one's genes to future generations. Industrial society has made some factors unimportant, for example, we no longer have a significantly greater chance of surviving to reproductive age if we can run faster than a lion or have good eyes to see a crocodile. However, evolution can still select immunity to childhood diseases, resistance to infertility, features considered attractive by the opposite sex, etc.
Evolution doesn't select anything. Evolution is an observable process that is driven by natural selection (and what we've termed artificial selection).

[benhur]

Neither of those articles explain why Africans are the most genetically diverse of all human populations.

How is this established?

[Devrim]

Neither of those articles explain why Africans are the most genetically diverse of all human populations.

The reason that Africans are more genetically diverse than the rest of the human population together is because humans originated in Africa, and a small amount left meaning that the rest of the human race outside of Africa is descended from only a fraction of the African gene pool.

Devrim

[DesertShark]

How is this established?
Comparing genetic sequences.
Also, read the following:

The reason that Africans are more genetically diverse than the rest of the human population together is because humans originated in Africa, and a small amount left meaning that the rest of the human race outside of Africa is descended from only a fraction of the African gene pool.

Devrim

[MarxSchmarx]

Hmmm... Hmmm... and Hmm...

I skimmed through the source article cited.

Merging demography with the kind of genome-scale genetics they did is a notoriously tricky subject. There are gobs of underlying assumptions, some well-justified others open to question. For instance, the increase of fixed mutations as a proportion of population size that they use is based on a derivation from 1930 that relied on, among other things, weak selection. Moreover, it's not clear human growth has been exponential over the past 5000 years (perhaps over the last 500), and between wars and famines and epidemics it's been quite a mess. And I haven't even begun to look into the shortcomings of the archaeological record as a proxy for population growth. The calculations more over are justified with laboratory organisms, which is a bit of a stretch.

Racial differences in things like skin color are present, but it is also not obvious how much of the genome is responsible for such racial differences. The authors would have us believe quite a lot. We still don't know how much dna we share with chimps (believed to be 95-99.9 %), much less each other.

Moreover, there is the very real problem of how geographic structure fits into all this. Humans are in many respects anomalous - they colonize areas rapidly, but they are quickly cut off from ancestral populations, as their is little gene flow between them and ancestors. Undoubtedly local adaptation plays a role, but how to reconcile such processes with the complex genetic geography of, for example, Africa, is not an easy question. I am not sure whether their indirect methods are really all that persuasive. They certainly are an intriguing pattern, and no doubt the rapid colonization of the planet has resulted in considerable evolutionary divergence than when we were one population or a group of populations living close to each other back in Africa. Finally, I think as a first cut this is a really interesting study and is scientifically meritorious for the patterns it highlights that do demand an explanation. The authors have taken a stab at it, and I give credit where credit is due.

What I find somewhat implausible is the strength of natural selection attributed to this divergence. That, I think, requires much much closer study than the authors have given.

All in all I think the authors are on to something, but I'm not sure if their measurements are as accurate as they claim, or their approach wouldn't produce similar findings in other organisms that recently colonized a geographically diverse area.