Human Evolution

As someone who has dabbled into evolution for sometime I am now interested in really grasping and understanding the theory even better so I will bring up another topic of interest. Specifically: human evolution.I just have a few brief and simplistic questions to start, forgive me if they seem silly:1. Why are all other Homo's in the Genus (except us) extinct?2. As we continue to evolve will there eventually be another speciation event where a group of humans become too genetically incompatible with another? Or since we are so great in number and widespread is this no longer possible?3. Regarding human origin and ancestry specifically the relation of Humans and Neanderthals: what common ancestor do we share with them? And how long ago was the split?I have searched the internet regarding these various random questions but I was just curious if anyone here with experience in relevant fields could help me understand further. I know these are completely random questions heh.Thanks.

Thread copied here from the Human Evolution thread in the Proposed New Topics forum.

Because they either were out competed or were unable to adapt to the environment.. Although I'm sure we can debate this. I honestly don't see humans evolving all that much over time. We adapt or environments to us instead of falling victim to it like other species. The only force I see still at work is sexual selection and even then most humans still will have a chance to reproduce... Somewhere around 600'000-500'000 years ago and I've read it was Homo rhodesiensis

It might have already happened. Can we be sure that the average H. sapiens of 2010 is interfertile with the average H. sapiens of 1510?

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I would argue that human evolution has happened in the past, is continuing to happen, and will continue to happen in the future. Natural selection, sexual selection, and the various pressures are only some mechanisms involved in the overall process of evolution. Just by having a population living in an environment, no matter how stable, evolution will happen. The mere fact that mutation is inevitable makes evolution inevitable.

The easiest way to get speciation is physical separation and different environments.Nothing I can imagine will do this better than space colonization at distances that permit only limited contact with Earth.

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Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

Yes. As evidenced by the last 500 years of mass migration around the globe, human populations that had been separated for thousands of years are still quite interfertile with one another.

I agree. Globalization, modern medicine and agriculture have greatly decreased the selective pressures remaining on the human race.It is estimated that 1.3% of children in the US will die before the age of 20. I believe this to be a good estimate of the number of offspring who will reach the age of reproduction. With the numbers this high I see it unlikely that there is enough selective pressure to cause enough evolution resulting in a speciation event.Compare this to Chimpanzees of whom only 60% reach the age of 7; where the reproductive age is between 7 and 15. http://www.unl.edu/rhames/chimprs/chimprs.htmThere would really need to be a mass pressure event or isolation in order to quell the mixing of human populations worldwide. Globalization has most likely also contributed to the mixing of human DNA across the globe. I see it unlikely that a human speciation even resulting in 2 distinct species would occur without a great increase in selective pressure.

Hi CosmicAtheist, I don't see any greater significance to the situation that three of four known hominid species have gone extinct in recent geologic history, than they could not survive in their environment. The fourth may be on its way to extinction as well in the same geologic time frame and possibly due to the same environmental influence; that being cultural. If humans were not so rapidly changed and influenced by our 'big brains' (Kurt Vonnegut's motif in Galpagos: A Novel) then I would say yes, there would come about evolutionary change to people. But, because symbolism and language has sprung up among humans, I too see as many others before me, that our genes are operating now within a larger framework of cultural change far more influential upon our future than anything else that genes or selection could cause.I was just reading the Wiki article on technological singularity. If you read it I think you might come to the same conclusions as so many others have about human evolution. Genes play a far less significant role in human development as memes play(ed).I don't know off the top of my head about your third point, but it must be an easy thing to find out. Did you know that a complete Neanderthal genome has been sequenced?Edited by CosmicChimp, : fixed title

Thank you all for the responses so far they have been very informative and CosmicChimp, my 2nd question was the one I was the most curious about, thank you for the article. I skimmed it and when I have more time later tonight I will read it more in depth.

It is obvious that many of us do not fully understand evolution. Please correct me if I am wrong.Evolution is descent with modification (Life can only come from life) and nature never has to start from scratch again right? Is this the correct interpretation in a nutshell? I realize that there is several factors involved in this process.
If true then the fact that I am here living right now, my ancestry goes back before I was classified as Human all the way back to the beginning of the first life on this planet. My line of descent would have many different names to describe who my ancestors were at any particular time frame in history. Humans evolved from many different lines of classification of humans, primates, and before that no one really knows due to lack of fossil evidence.
In other words the only way for me being alive today is because every generation in history lived long enough to produce the next generation that goes back to its origin.

Actually almost right. Pretty good as a matter of fact. It's possible, even likely, that life started several times, maybe even many times. It's also possible, likely even, that life could begin again, even today, BUT, unlike that time long, long ago, now there is other life forms that are occupying all those niches and would simply see any new life forms as food.The earlier attempts had a chance, they did not have to face being eaten by the billions and billions of hungry critters that are out there now. Yup. Almost. We don't know all the specifics but actually have a fair idea of the lineage and are learning more every day. Yup. Every line that did not reproduce became a dead end.

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Thank you for not making me feel stupid and answering my question in a direct manner.Now that we have established that my whole line of descent is firmly rooted in the tree of life's origin, would my DNA support this? Or through its course in history the genes used in the beginning have been deleted or changed for modification as time moved on so it would not be a reliable source?

Not sure what you are asking here. Reliable source of what?

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Facts don't lie or have an agenda. Facts are just facts

It certainly confirms parts of the direct descent idea.Remember, our knowledge of DNA is just beginning, we still have a long way to go.BUT, the important thing is that until we got some detailed specs on our DNA, the connection even between humans and all the other primates was based on morphological inference.What we are learning from DNA is simply another independent confirmation of the Theory of Evolution and Common descent. It's that additional confirmation, one from yet another whole different area of knowledge and methodology, that simply added even more weight to the Theory of Evolution. Not sure what you are asking there. Do we have examples of the first DNA? No, of course not.Will comparisons between DNA from different critters and plants help us understand our lineage? Certainly.

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Anyone so limited that they can only spell a word one way is severely handicapped!