Discussion of everything related to the Theory of Evolution.
As many biologists know, evolution by means of natural selection will act on the specific handful of individuals from a species who decide to live in a different habitat, among many other causes for evolution by natural selection. These few individuals will evolve via natural selection which will result in offspring becoming more well suited to their environment. A good example is the evolution of the whale. As many probably know, the whale evolved from a wolf/hippo-like creature. Some members of this ancient species decided, because of food competition, that food may be obtained easier in a body of water. The few creatures that decided to swim for food evolved via natural selection into whales after millions of years. Wolf-like creatures are obviously still in existence because only a few decided to look for food in the water. Natural selection only acted on the few who hunted for food in the water.
With the evolution of the human, a good majority of biologists believe we evolved from great apes, also known as hominids. The ape obviously still exists today, meaning only a specific handful of apes must have evolved via natural selection into a human being. Just as whale evolution had the "trigger" of food competition in several wolf-like creature millions of years ago, can't we also assume human evolution also needed a "trigger" in the ape? Just as the wolf-like creature decidedly did something "different" for food consumption which allowed evolution into the whale, did a handful of great apes decide to do something "different" that allowed natural selection to evolve apes into a bipedal (meaning walks on two legs) creature that is also the most intelligent creature in history? Clearly, wolf to whale evolution acted on physical traits. But ape to human evolution acted very much on our intelligence, also. In only several million years we went from ape to being able to create computers and cell phones, which is unimaginably unique to the history of all life on Earth. The actual modern form of human is roughly 1/4 of a million years old. Once again, what did a handful of apes do differently that allowed natural selection to evolve those apes into a bipedal human with impossibly unique intelligence?
I will appreciate all feedback, thanks.
Last edited by jasonP on Tue May 13, 2008 3:42 pm, edited 2 times in total.
For the most part your reasoning is sound, except I dispute your claim that we went from ape to today in only 250,000 years. I may be wrong, but I am certain that the last common ancestor between apes and humans lived around five million years ago. Still a remarkably short time in geological terms, but much longer than your estimate of only a quarter of a million years.
That said, I think competition for food and/or habitat was the biggest factor. It's been a while since I read up on this, but as I understand it, the ancestors of modern humans evolved from apes that had lived in forests but then moved out onto the plains, where they would eventually evolved into humans. I do not know if anyone has seriously contemplated the question as you have, but it seems to me that competition for food and space in the forest would've been a very good reason for our ancestors to take their chances out on the plains. I've read that bipedalism evolved to allow hominids to stand taller and thus see over a greater distance and thus be able to detect predators sooner. Once this freed up the hands from having to be used for locomotion, this allowed the first serious use of tools, and then motivated the evolution of an intelligent brain capable of producing and using these tools. Once these factors are in place, give it a few million years and you've got a human.
Generally speaking, the more people talk about "being saved," the further away they actually are from true salvation.
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Thank You! You're logic makes sense to me. It does make sense the ape needed to migrate to have more space and food consuming capability. So from you're viewpoint do you believe the "trigger" was also food competition but with a need for space?
Also, I did make a mistake in my original post. When I wrote 1/4 of a million years I was thinking that this is how long humans have been the modern form. Yes, you are correct, it took several million years to go from ape to human. I will edit that mistake, thanks for pointing it out.
It makes sense to me that competition for food and need for space go hand-in-hand. Both are the effects of overcrowding. I don't think one can exist without the other. So I would say the evolutionary "trigger" was overcrowding in the forests where the apes lived.
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I also think another issue is female sexual selection. Females were likely attracted to more intelligent males and mated with them. Or perhaps the females never detected intelligence. Maybe a more advanced tool resulting from intelligence helped to bring more food and shelter to offspring. The female, therefore, was more attracted to those "services" the male provided from the more advanced tools which stemmed from increased intelligence. Females then would mate with the males who provided those "services" and the allele for intelligence would become passed on while an allele for lower intelligence would "die out" as those males never recieve the opportunity to reproduce. That is my opinion. None of this is really fact of course. I am making sense of all this as I go along.
Also, I believe some apes can extend their thumb to their other four fingers. This trait deinetly allowed for grasping and tool development. Perhaps the allele for high intelligence exists in many animals and it can only develop if a limb can actually grasp tools. What is you're opinion?
I think the opposable thumb developed after bipedalism allowed the hands to be free for tool usage, as an adaptation to making and using tools. I don't doubt that sexual selection played a role, but if it acted as you describe then it probably didn't take effect until after human ancestors had left the forests, and thus after the "trigger" had been pulled. I think the trigger itself must have been overcrowding.
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Wow this is a great topic! I think the logic in all of your posts is really good and, well, logical. It is an interesting query about the 'trigger'. While I agree that the over-crowding and resource competition makes sense, I can't help but wonder whether there was something more, as I would have thought that life on the ground was quite perilous at the time. Could it have been an environmental factor? For example, something happening to the trees or a drought that caused them to search further for water until the only practical thing to do was to stay on the ground. I think I have the least scientific knowledge of the three people who have posted on this topic so please don't yell at me (virtually) if I've said something really stupid, I'm quite happy to take criticism and discuss/debate the issue
My memory isn't very good on the subject (as I said I need to read up on it again), but I think there was a major environmental change at the time the first humans started evolving. If I remember correctly, a decrease in annual rainfall caused large areas of forests to become plains. If there was less forest available, then this may have increased the overcrowding problem, and caused our ancestors to seek new opportunities in new environments.
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Morgyn and Alex you are both correct. Major environmental changes were occuring a few million years ago and directly impacted human evolution. Researchers believe major dry and wet spells rapidly came and went. The big question is did the dry spells make early humans evolve into homo-sapiens or was it the wet spells. The link to this article gives a fine explanation.
http://www.guardian.co.uk/environment/2 ... .evolution
I would think it would be dryer weather. Aren't plains and grasslands associated with dryer climates than forests?
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If you're looking for a trigger, I would suggest bipedalism allowing the carrying of babies. Infants no longer needed to be born with the coordination and capabilities to ride on a moving mother, and could spend a couple of years in brain development beyond the womb.
That's a good thought, but how would it come about through natural selection? Would the fact that the babies that could not hold on better were no longer more likely to survive mean that there was a more equal chance for all babies, with the more intelligent eventually being selected? Hmm....
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