A species “perfectly” suited to its environment will not evolve. Mutations can occur, but they would always have a negative impact on survival when compared to members of the species that are “perfectly” suited to an environment. Man is, for the most part, largely in control of its environment and therefore pretty damn close to being perfectly suited to the enviroment that it has created for itself. Because of civilization, almost any gene can be passed on to the next generation. Without a radical change in the world as we know it man will not evolve in any significant way.
Penicillin and its ilk have been used to reduce infections and counter disease for less than a century, and already several strains of higly toxic bacteria are evolving to be resistant to these lines of attack. A nice, vancomycin resistant strain of e coli gets out there and we’re in trouble.
Outbreaks of Ebola continue to occur in Africa. We continue to be lucky in containing them. It is probably a matter of time before some lucky vector to another part of the planet starts an epidemic.
Global travel means diseases spread further and faster than ever before. Take a look at the way the AIDS crisis made its way across the planet. 2/3 of the Earth’s population doesn’t have access to clean drinking water. How can we expect to combat a global epidemic given these facts? We can’t.
Those of you who insist we are “largely in control of our enviroment” know very little about epidemiology.
As for the first quote, what do you mean by “given current conditions”? It’s like saying “as long as nothing changes, nothing will change”. Don’t count on nothing changing.
Let’s stipulate that the premise is true, that humans are perfectly adapted to their environment, and that every human will have exactly the same fitness as every other human. Well, this gives us different evolutionary pressures than before, doesn’t it? Before, humans were selected for disease resistance, strength, sexiness, fertillity, etc. Now, this does not happen. So alleles for these different things will spread, since there is no selection against them. Evolution is defined as changing allele frequencies in the population. Ergo, evolution will occur. Humans will lose their resistance to disease, genetically caused infertillity problems will spread, the frequency of congenital defects will increase (albeit more slowly than one might expect, given that they are recessives).
So evolution will continue, just not in the way one might naively expect. But of course, one can see that the stipulation makes no sense, even when we exclude genetic engineering or artificial selection. Of course people with genetic diseases will have a lowered fitness than those without. Those with genetic fertillity problems will have fewer offspring than those with no fertillity problems. People will still die from diseases, just different ones…I imagine in the future there will be more people in africa who are HIV positive but don’t develop AIDS because lots of people susceptable to AIDS are going to die there.
For evolution to occur, a few things need to happen.
The population has to vary
That variation has to be able to be passed on
There must be differential rates of reproduction between the variations.
We can easily see that the human population varies. We can see that a portion of that variation is heritable. And we know that different variations have different fitnesses. Ergo, humans are still evolving. Now, humans a million years from now may superficially resemble humans today, or they may not. But there will be profound differences.
I read recently that a likely future change in the human (and other mammals’) genome could be the loss of the Y chromosome. Having it is a significant liability because it results in sex-linked genetic diseases. I understand that some mammals have already lost it.
Losing the Y would probably not cause any overt change to the human body though.
Ren, how about this: an antibiotic-resistamt strain of XYZ bacterium emerges and “we are in trouble”. Like in the Middle Ages, when 1/3 or more od European population died of plaque. Individuals nuturally resistant to the pathogen will survive and their progeny will be resistant. The species will survive. “The trouble” will be over. Till next time.
There would still be males. It’s just that the mechanism to create males would be on another chromosome and be different from the one on the Y chromosome.
From what I gather, the gene that causes a person to be male is a strange thing (compared with other genes) that has taken over the Y and made it a unique object, i.e. with no matching genes on the X. There’s only a few other genes on the Y, and they deal mostly, if not entirely, with features specific to males. So these genes would have to jump to another chromosome.
If we lose the Y, both males and females would have two X chromosomes. In other words, it would become just another autosome.
I would have phrased it like this: The survival of the species is contingent on reproductive success of individuals of that species.
The “little change” they undergo is relative; other major groups have changed much more over the same time period; and it generally refers to overall body plan/morphology. They may have undergone considerable change of internal, biochemical, and behavioral characteristics. For example, I’m sure their immune systems have changed so they can deal with modern pathogens. “Living fossil” is a very loose term to be taken with a grain of salt, not literally.
Sure, although Lemur866 already did a good job of this.
(1) Humans are not perfectly suited to our environment as it currently stands, which is why we constantly struggle to control it. Although we have great ability to change the environment, we do not control it.
(2) The environment will change. Ice ages come and go. We’re altering the ecosystem we depend on. In the very long run, the sun’s energy output will become more and more uncomfortable.
(3) Other species will evolve & challenge us (e.g., pathogens). Individuals of our species have varying immunity to germs.
(4) Evolution occurs over millions of years…a “radical change” is commonplace over such timeframes.
(5) A species “perfectly adapted” (if there is such a thing) will still eventually evolve due to some of the other evolutionary forces I mentioned…survival of the fittest is not the only thing at work here.
(6) Not all mutations are negative (most, but not all). Gene mutations are considered a means to increase genetic variation. Variation among a subset of a population can spread to the entire population given enough time.
(7) Evolution does not have a perfect model species. It is change. As environments change, what is considered a beneficial trait changes.