natural selection

"Natual Selection" deals with the continuation of the gentic line. Hair length and left-handness aren't genetically coded (If it wasn't for our individual intervention we'd all have long hair!)

Being more prolific is a natural tactic to attempt to continue the genetic line. The trait is very common in any species when the average life-span is short. As the average life-span increases the number of off-spring per individual drops.

A few of the less important but intereting questions are these:

Why can't humans produce Vitamin C (ascorbic acid) in their bodies while almost all animals can?

Why humans became almost hairless?

or

Why each hand has five fingers (in the usual cases)?

Why two kinds of sex not three, while DNA has four types?

..

Good points Satt-, however DNA does not have four "sexes", nor does any other organism. I suppose you might say that aberations count in certain cases, like the simple life form that can be either female or male, but then that isn't three, it's one or the other. By the way, what are your thoughts on the biological functions or origins of homosexuality? Ciao, Dov

Dov- You don't have to drag emoticons. When you come to the place in your reply where you want to put one, just left click on the one that you want, and it will appear! :wink:

I do not mean aberations when I say a (supposed) multiplicity of sexes, i.e., three or more sexes. You can imagine a group of ET's where a hundred of sexes are engaging in reproduction.
I do not say four types of constituents of DNA is any kind of sex. I referred to them as an analogy.

It's not that the fittest are selected for, but that the least fit are selected against -- that is, they fail to produce viable offspring. Without any factor selecting against a particular trait, it is retained. The appendix no longer serves a function, but it is still there. Likely it will eventually become less and less prominent and may vanish altogether in individuals and then in populations because there are no selective pressures against people born with minute appendices.

On the other hand, if there was a worldwide epidimic of some virulent and deadly disease that could only survive in the appendix, the surviving population (if there was one) should be appendix free or resistant to the disease.

We fight against Survival of the Fittest to the extreme everyday. Doctors operate on fetuses, keep people in comas on life support for years, spend billions of dollars in research and medical care for children that would not survive 24 hours after being born, the list goes on and on.

You can feel that these are technological advances that you wouldn't deny anyone , but such cases are not truly fit to live on their own. These are just physical examples and doesn't include people who are mentally unfit.

I'm not professing decisions on 'what would I do' or 'who am I to judge'. I'm simply saying that as humans we generally practice survival of all, not the fittest.

Some women are bald. Does this mean something relative to natural selection, when these very women can go out and buy a wig?

Back to the idea of "Natural Selection"...Phenotype plays a dominate role in determing destiny. Ask any unattractive human male or female.

Sugar -- it is true that we work against natural selection, in a way, though the examples you provide don't increase the chances of survival of those individuals' genes. In fact, they frequently suck resources away from the offspring of individuals on life support, making them (theoretically) less capable of reproducing and thereby decreasing the chances of survival of the patient's genes. On the other hand, while we might mediate against selection against, say, childhood diseases or compromised immune systems, we also express and strengthen the social and intellectual faculties which have enabled our weak, soft, hairless species to propagate as successfully as it has.

New Haven -- yep, very true. And it's not just humans, either. A peacock's massive tail feathers place it at a tremendous disadvantage; many calories must be consumed just to grow and maintain it, to say nothing of the impediment it must present in eluding potential predators.

It's been noted in several bird species that females are attracted to risky behavior and display. There is a species in Israel -- I think it's some sort of sparrow, but I don't rightly remember -- wherein the males have a tendency to taunt their predators. A bird of prey swoops down at them, and rather than heading for shelter right away they will flit back and forth in the open until the last possible moment. The males who exhibit the most daring behavior in this respect tend to be chosen as mates by the females, and so the behavior is passed on to succeeding generations. Such behaviors are not uncommon in the animal kingdom.

The researcher who noted this has been hard-pressed to come up with an explanation. His notion, if I remember rightly, was that only the most robust individuals are capable of displaying such behavior. A courageous clumsy bird would be eaten.

At any rate, though, we are at a very stable place in the evolution of life right now. Just about every niche is filled, and until something happens (asteroid? global warming?) to cause a mass extinction and re-open currently occupied niches, there's not going to be a great deal of diversification and speciation.

What's a phenotype New Haven?

The phenotype is the resulting individual. It is the sum of all the bodycharacteristics that interact with the environment (red hair, big ears, sense of smell, speed brain, hair etc) , as compared to the genotype, whiich is the compliment of genes that an individual carries.
This is paraphrased from Ernst Mayr.

Patiodog-since evolution is often like watching the hands of a clock, you might say that all is in stability. (One of Gould and Eldredges periods of stasis) However, if you look all over the world, you see that all kinds of speciation is occuring to many different species and higher orders. For example, the rufous hummingbird has , by interaction with humans and birdfeeders, established a population(that is almost a subspecies) of Eastern rufouses. Theyve done this by learning to migrate south and east.
The red wolves of the Afar are gradually changing intop 2 subspecies separated by the geographic isolation brought on by the breaking apart of the Rift valley .
There are a whole bunch of guys out there working on cladogenesis by screwing around with populational statistics through time and through geography.

Id love to be able to come back in a million years or so and see (of those species that remain) what they would look like and as species go extinct , what has taken their place.

Saltation , or "punctuated equilibrium" is not too much in fashion anymore because a number of scientists have been doing detailed sampling along long and short geologic periods, and they are discovering that intermediate species do occur. Once an organism makes up its mind to become something else, aint nothin gonna stop em, and they leave evidence of intermediate fossils all over the place.

Am not meaning to deny that evolution does not occur during catastrophic events. I haven't heard anybody talk about punctuated equilibrium who contends that the "equilibrium" part of the phrase be taken seriously -- just that we are not living in a period of tremendous diversification, as you had with, say, the radiation of mammals. (Clearly you've read a great deal more on this; I'm a neophyte. I answer back solely to keep up an end of a conversation.)

Since on the subject, though...

Where I grew up there was occurring a very interesting phenomenon, in terms of natural selection. There are (at least) two very distinct populations (or subspecies, depending on who you ask -- splitting hairs, that is) of mule deer in central and northern California. One is native to the central valley, and the population sports a gait that is suited to a flat, largely treeless plain. The other is native to the foothills and mountains, and has a gait that is suited to hilly, forested terrain.

In recent years, as the foothills and valley have become more and more populated with people, there has been an explosion in the deer population and their traditional predators -- chiefly mountain lions, though I suppose black bear may have played a role, as well -- have declined. As a result, the deer from the valley and the deer from the foothills have come in contact with each other a great deal more than they used to, and are mating. The resulting offspring have a gait that is suited to neither forested hills nor open plains. Without any selective pressures against the population outside of cars and the fickle pressures of sexual selection, this gait (last I heard) has been become more and more pronounced in the population. The unfit have survived as well as the fit -- though the former will only be truly unfit if a significant predator population is re-introduced...

Reading....

I have had a nagging question about natural selection all my life. I just can't figure it out. It can be assumed that the most "attractive" people are the ones that tend to produce more than the body of people considered "unattractive". Why is it that there are so many ugly people in the world? I'm serious. My parents were well known for being very attractive while young. All four of their children are average looking. I know the excuse, and I can't fall for it, that is that standards of physical beauty change over the centuries. I don't buy it. There is, in my opinion, a general definition of attractiveness that survives thru the centuries. I know it is subjective to some extent but why do all those ugly genes keep hanging around? Ciao, MIKE ANGELO

recessive genes

I was at a restaurant the other day and there was a particularly startling family. They had a variety of physical unpleasantnesses in a range of combinations. The dad, the mom, the brother, the older sister, all were what would unhesitatingly be called ugly. But the younger sister -- while there was still a clear family resemblance, it all came together perfectly, and she was just beautiful. Her dad's nose without his weak chin -- her mom's blue eyes without her giant beaked nose -- the eyes neither too close together nor too far apart -- everything balanced.

Looks-wise, she will probably be considered great genetic material by a future mate. Then they have kids...

ha! it skips a generation!



anyway, so, what -- ugly people can't procreate? it ain't like there's a selective pressure against ugliness; maybe if we exceed the carrying capacity of our habitat and the population we can get rid of those damn uglies (and my line will likely end).

whatta resurrection...

Right, I was gonna make that point -- what's so bad about being ugly? There are aspects of beauty/ugliness that point to less skin-deep conditions; the ideal 36-24-36 figure is supposed to indicate maximum fertility, etc., etc. But a big nose -- how does that effect survival?

And one other thing -- it's not like physical desireability is the only reason people choose their mates. There is personality (Woody Allen, say), money (Donald Trump, say) power (Mussolini, say), etc., etc. Physically, all of these people are far from prime specimens, but they get/got the chicks.