A discussion we had around the water cooler here at the office was if people have stopped evolving.
I say we have stopped because we’ve removed the key factor, environmental pressure. Evolution is supposed to happen in response to external pressure - the ability to adapt to these pressures will decided if you get to pass that ability on to future generations.
I think we’ve learned instead to adjust our environment to us and have therefore short-circuited the evolutionary process.
The folks that disagree with me here seem disappointed that we’re not going to evolve bulbous heads or into energy creatures as depicted on Star Trek.
So - while this may be an IMHO or even a GD, what do you think? Are we at an evolutionary dead-end?
No. Humans have not stopped evolving. Not everyone has offspring and of those who do, not all have the same number of offspring. We still have external pressures, and we still practice mate selection.
No, we haven’t stopped evolving (although I think it’s less apocalyptic than Dr. M does). However, things have changed a bit.I don’t think we’re speciating any more; I don’t think any radical changes are in our future.
Evolution used to be propelled by survival and mating; if you die before reproducing, your genes are out of the race. If you mate a lot, you will reproduce and your genes will prevail.
Nowadays, survival is a minor part of the picture. Most viable offspring survive long enough to reproduce dozens of times, so mating takes on the larger importance. Mate selection in most human societies reflects health and sexual characteristics; the number of offspring depends on mating and reproductive choice.
So, to judge by the media, we appear to be selecting for taller men and women with larger breasts (or maybe we’ve leveled off). We are selecting for whatever characteristics are shared by people with large families. Most of our choices are pretty conservative, so large changes in the human form seem unlikely.
I’ll buy that we may be selecting for characteristics shared by large families but the first sentence doesn’t seem quite right.
Stupid people have children, flat chested people have children, short people have children. I don’t see how the media ideal of large-breasted tall folk affects the next generation.
I’ve always wondered about the “spreading” of characteristics. Since tall people tend to marry tall people (making taller children) and short marries short (making shorter children) then perhaps we’re breeding away from an average.
There’s got to be something to the fact that we’re propagating the tendency for fatal diseases, too. Things that would have killed in childhood a hundred years ago have the increased likelyhood to be passed on today. Are we weakening the gene pool? Adding variety?
I’m sure most folks have an annecdote about a relative marrying someone a foot shorter or taller, so I won’t share mine. The point is, though, that even if folks with similar traits have a tendancy to be attracted, there’s still enough intermixing of any given sort to keep us all tied together as the same species.
Interesting thread. Here are a couple of thoughts.
First, how will we ever know if we have removed the key factor (Belrix’ environmental pressure)? We can’t look back at the 1800s and compare because it just doesn’t happen that quickly. Evolution needs a couple of key ingredients: 1) enough variation within a population to ensure different levels of reproductive success and 2) time. I submit that with 6 billion people on the planet, reproducing at an alarming rate, the number of potential genetic mutations within the general population is increasing rather than decreasing. Whether these traits are being selected for won’t be clear for another 20,000 years.
Second, I agree that through medicine, nutrition, and technology we have removed many of the barriers that had previously prevented large numbers of people from reaching their reproductive age. However, this brings up my initial point again. We cannot discount the evolutionary process simply because we can’t see it actively working. I believe that in the future, humankind will look back and see that the Homo homo sapien population has been shaped by two things: 1) differential levels of resistance to bacteria and 2) (in)ability to absorb UV light. Anyways, that is my guess. If the SDMB is around in the year 22002, y’all can check and see if I’m right!
Finally, as far as speciation goes, I have one word for you - transportation. As long as our populations are connected, then there no chance for speciation to occur.
Anyway, even if we removed all selective pressure, THAT would be evolution, since the absence of selective pressure would be a different selective regime. Removing selection pressure would cause a change in allele frequencies as deleterious alleles are no longer removed.
The trouble comes when people get confused about the meaning of the word “evolution”. People tend think it implies some sort of teleology…the human species getting better, or moving to some goal. But all it means is changes in allele frequencies. And that will always occur, even if just through mutation and random drift.
Well there’re a bunch of different ideas about how evolution happens, but one (Punctuated Equalibrium, IIRC) says that for thousands or millions of years there is no major change. Varibility increases as recombinations, mutations, etc. develop in the population until a major challenge occurs (flooding, drought, meteor, etc.) that provides the selective pressure.
Evolution isn’t a directed process. There’s no “forward” or “backward” except for our imposed subjective ideas. We’re not “more evolved” than (other) animals, just different (as they are). I’ve heard social evolutionist arguments that we’re making out species weaker by ‘allowing’ weaker individuals to survive. I’ve also heard that were making our species more prepared for the same reason (providing more genetic variability to meet whatever challenge occurs in the future).
If you looked back over the last 100 millions years or so and checked populations of animals or plants at random time points, you’d probably find they weren’t “evolving.” You’d have to look over long periods and say evolution had occured over the period.
Even acknowledging their premise, though, the argument doesn’t hold up. For example, someone who is nearsighted or diabetic might also have genes that are better fitted in other ways, and by keeping them alive with eyeglasses or insulin, we add more diversity to the human genetic possibilities.
I’m not sure that this is evolution, but both my parents had “12-year” molars and wisdom teeth, and the wisdom teeth had to be removed because of lack of space. I did not get the molars, but I got wisdom teeth, which didn’t need to be removed, since I had not got the molars. (I don’t know the difference, but it’s what my dentist told me.) The x-rays showed that I didn’t have the molars in my head at all, not that they were there but never developed. The dentist also said that each generation sees fewer people with the early molars, because we don’t need them to crunch bones and such anymore, since we’re living more and more on sandwiches and Twinkies.
Could it be said that the gradual disappearance of molars is a form of evolution?
Yes, I know that wisdom teeth are molars; I think the guy told me that they are a distinct kind of molar. And it may just be simple variation, of course. I just wonder why that particular variation is (according to the dentist) more and more common with each generation.
C’mon, Darwin’s Finch, don’t deny me the opportunity to feel like I’m on the cutting edge of evolution! I don’t care what anybody says, I’m part of the New Order.
The confusion comes in because people think “evolution” is a process that defines our way along a set goal. That evolution starts with bacteria, and ends with super-intelligent energy beings. This premise is simply false. Evolution has no goal - it simply is a process by which a species becomes more adept at surviving in their environment.
People seem to think evolution is something that just happens over time… that in a few thousand years, no matter what, we’ll be that much closer to our ‘ideal’ form - which seems to be big-brained star trek creatures, or energy beings, or something - and that’s just silly.
Humans aren’t really involving in civilized countries in the traditional sense - we don’t survive or die because we could or couldn’t kill animals, escape from predators, etc. By definition, any change we make that helps us adapt to our current situation is evolution - but there aren’t really genetic advantages and disadvatanges in society so much as social ones, and so evolution in the traditional sense is basically on hiatus. You could argue that being a welfare mom with 20 kids is what we’re evolving to
How do you know compassion isn’t a behavioral adaptation to increase survivability? Remember folks, behavioral traits can be modified by evolutionary processes just as well as physical traits can be.
