Humanity as an evolving species

Pardon me if anything about this thread goes against the local forum etiquette, or if this is the wrong place to discuss such a topic - this is my first post, and I’m afraid I’m just too impatient of a person to spend enough time lurking before posting that I can be sure that this will be well received. I hope you’ll also pardon me for using quotes from Wikipedia - I don’t do this because I value it as a source of information, but simply because a lot of well-known and generally accepted information is organized and explained in a convenient manner on Wikipedia.

Many of you may be familiar with the idea of Adaptive Radiation in Evolutionary theory. Adaptive Radiation is “a rapid evolutionary radiation characterized by an increase in the morphological and ecological diversity of a single, rapidly diversifying lineage.”

Adaptive radiation occurs when a species is introduced to a new environment in which it can thrive; driven by natural selection, it is the process by which a species splits and evolves to fit all of the available niches in its new environment.

Most evolution happens in a pattern called Punctuated Equilibrium. Punctuated Equilibrium is “a theory in evolutionary biology which proposes that most sexually reproducing species will experience little evolutionary change for most of their geological history (in an extended state called stasis). When evolution occurs, it is localized in rare, rapid events of branching speciation (called cladogenesis).”

One of the best indicators of whether a species is in a state of stasis or not is the population growth level; a static population usually has little change in population size. However, a species which is evolving rapidly, especially during an adaptive radiation, will experience exponential population growth.

Human population growth, over time, looks like this:

Therefore, I submit the following for your discussion and consideration: The human population on Earth is currently undergoing an adaptive radiation, and is evolving to fit all of the niches available. Until population growth slows significantly, humanity, as a species, will continue to change rapidly.

If we assume this statement to be true, we can look further to determine what aspects of what populations of humans are evolving. For example, in the Western developed world, physical traits have very little to do with survival. It is very rare that a person fails to survive and pass on his DNA simply because of his body. However, the differences between the minds of individuals do have a great influence on who does and does not survive and pass on genetic material.

Therefore, I submit the following for your discussion and consideration: in the Western world, humans are evolving into different sub-species, which may eventually evolve into different species, based on psychological differences.

Quotes from Wikipedia

welcome to ILP.

interesting post. i have to ask, though, what the mechanism is that the psychological evolution operates through… in the western world as well as most everywhere else, psychological factors dont seem to impact breeding potential. there are just so many people out there, most of us find someone to mate with.

so what specific factors that are psychological do you think are serving as a medium through which natural selection is acting? i cannot see overall intelligence as a factor here, as it seems stupid people and smart people (and everywhere inbetween) have kids all the time. basically material success or wealth has no bearing on the ability to reproduce, therefore any psychological traits bearing directly on material success or wealth are, from the perspective of evolution, useless.

i also dont really see us as going through an adaptive radiation at the moment… yes we are exploding as a population in total, but this in and of itself does not mean we are branching out in a supersaturating of available niches. im not saying that we arent finding new ways to adapt to old niches, just as im not saying we arent creating new niches all the time and then filling them (we are), but i dont see this behavior as evolutionary in a natural selection sense. we have just reached the state where our ability to manipulate environments is so high that we actually CREATE our environments to suit us. naturally, in a perfect environment (one with plentiful resources and all needs met) reproduction will flourish; and yes, granted we are not in such a perfect environment, but i argue that relatively speaking we are close. food, water, shelter are plentiful in much of the world today. even in the third world there is sufficient food and water to sustain massive population growth, even while there is extreme poverty.

so basically i just see no evidence that we are really evolving that much, if at all, at present. yes im sure we are changing in many ways, and the mixed breeding of differeng races and traits which is taking place on a massive scale is bound to have significant effects, but most of those will be random in that those effects do not bear directly upon reproductive ability itself. i dont think we are evolving or adapting very extremely at the moment, i just think we have found an ‘environment of plenty’ and are on the way to filling it with naturally, with the maximum numbers of our species which these new environments can sustain.

and btw, this thread would be good for the Natural Sciences forum, but im sure a mod will move it if its a big deal.

I’ve actually had similar thoughts to yours, Brandon - that we’ve reached a point in our evolution in which we don’t really need any additions or changes to our physical makeup, and that the nervous system is so versatile and maleable that it can adjust to any changes in the environment as a means of changing how the body reacts to it overall in a survival inducing way (we’re like a swiss army knife in that regard, and it’s as if it were hooked up to a computer governing how it’s used - it’s really the computer that needs reprogramming in order to handle any changes, not the features the swiss army knife comes with).

On the other hand, I’ve also considered how readily the human brain configures itself in response to changes in the environment - that is, how readily it does so holding genetics constant. In other words, we may not need any genetic mutations in order to adapt to changes in the environment - not even at the level of our psychology - since our genetic underpinnings are already built to adapt our minds to change quite effectively. We learn to adapt. I’m not saying its a universal solution to any kind of environmental challenge, but it sure goes a long way compared to a species whose nervous system is more or less fixed.

As you said, “we have found an ‘environment of plenty’ and are on the way to filling it … naturally”. I agree entirely - however, in nature, the means by which an environment is filled naturally is that the population grows until the death rate or birth rate changes to even out the population size - in other words, either less individuals will be born or more individuals will die until the state of “equilibrium” which I described above is reached.

You raise a good point, that we’ve gotten to the point where we can manipulate our environment to the degree that just about everybody can survive and reproduce. However, our population can’t grow exponentially upward forever. Eventually, either the birth rate will have to drop, or the death rate will rise. This is because the Earth can only support a certain size population.

I don’t know what that size is, so it’s hard to say whether the population growth rate will start to slow down seriously in 10 years or 100, but it’s bound to happen eventually. I’m not sure of this, but I believe that the rate of acceleration has already slowed down; that is to say, the population size is growing, and the rate at which the population size grows is growing, but the rate at which the rate at which the population size grows is decelerating. It’s kind of hard to think about, but the conclusion that I would draw from that information (if it is, indeed, true - for I can’t remember where or when I heard that) is that we’re nearing the “halfway point” at which the population will stop growing so fast and start evening out.

With that in mind, you’re still right that there’s virtually no competition currently, because almost everyone survives and can reproduce. However, we are “fanning out” in our discovery and exploitation of new niches. If we assume that eventually survival will get more difficult, we might infer that at that point the “fanning” will sharpen into “branching”, so that people could be categorized into very specific niches, and those who don’t fit in a working niche don’t survive. If this were the case, and if it was difficult to “jump” between the niches - that is to say, if it was difficult for a person born into one niche to leave and join another one - then we might see some reproductive isolation.

At this point, you’re probably wondering what exactly I have in mind when I speak of these niches. The truth is, I don’t know - I’m only applying observed trends in animal evolution to potential future human evolution. However, just for example, we might be divided up by reproductive habits - there might be one group of people who tend to have a lot of children, despite a high death rate among children. In contrast, there could be another group in which the average mating pair has only one or two children, but puts a lot of care into making sure that the children survive. There could be similar separations in other methods of dividing people, such as career choice, economic class, political views, and just about any observable lifestyle habit.

It’s true that we don’t currently see people being divided up into niches like this. However, we also don’t currently see a lot of people dying before they reproduce (or before the point in their lives where they could reproduce if they wanted to). If and when death rates do rise, I expect that the “fanning” into different niches that we can currently observe would morph into more of a “branching” process, as described above, which would be comparable to adaptive radiations in the evolution of animals.

Of course, this entire idea assumes as a given that death rates will eventually rise to surpass birth rates. None of this will even be applicable if the human population of Earth learns to lower its birth rates so that the population size could even out without an increased death rate.