After reading the article given to you in class (can also be found at www.actionbioscience.org/evolution/johanson.html) you should do the following:
1. Describe 2 concepts we have talked about in the evolution unit and how they relate to human evolution.
2. Pick 2 points in the article you found interesting and explain why.
Due Wednesday, March 9, by midnight.
Comment on something someone said by Friday, March 11, by midnight.
6 comments:
From the top of my head, I can say that I recall allopatric speciation and how it might have played a role in the development of Neanderthals. One of the theories they became so distinct is because of geographic isolation, and unless I read the source incorrectly, they didn’t interbreed with any of the overlapping sapiens. (They might have borrowed tools and skills, but not much more). This means that their genes would have (really sure they did) died off long before now. One of the only things I didn’t find quite right with this situation is how the Neanderthals were replaced. They just died off as their populations were replaced by the invading modern humans. I do find the Out of Africa theory to be the more trustworthy of the two, but that’s just because there’s so much more evidence that can support it.
At one point I think the article made reference to the concept of natural selection either with the earlier hominid species or the Neanderthals, but that would be one of the major factors of change over time. I find it’s interesting that our type of species developed the way it did; as others did I’m sure. We sprang up with newer species here and there it seems, but we didn’t develop from one of any of the earlier species. It reminds me of the misconception that a lot of people have about the “missing link” between apes and humans, from the becoming human assignment. I found it very interesting toward the end where the conclusion stated “humans have proven to be remarkably successful, culminating in our dominance of the planet at the expense of all earlier hominid populations.” We replaced the others, so does that lead anybody to wonder what, if anything, will replace us in the future?
One concept that was talked about through the Multiregional Continuity Theory was behavioral isolation. It has said that the transition from an uncreative species to a technological, artsy species was created is due to behavioral isolation. The change in family and social structure could have brought about this change. Genetic evidence is talked about a lot through the Out of Africa Theory. Genetic evidence through DNA is thought to be the most conclusive evidence in discussing common ancestors. The basis of the Out of Africa Theory is that genetics supports the theory through looking at the different Homo species.
I found it interesting the fact that Homo erectus migrated from Africa all across the Europe and Asia continents. I wonder what made them want to move away from Africa. Also, I wonder if the species able to survive in high numbers due to the different climates. If they did not migrate, how would we be today? I find it interesting how there is evidence to support two theories on human evolution. I think there could be a way to incorporate both theories in some way. All the evidence has to link up to one conclusion on how humans evolved. Or it could be both. It would be interesting to search more and find the answer.
This article talked about gene flow, which is a concept we talked about in class. The article stated that the level of gene flow between geographically separated populations prevented speciation after the hominids left Africa. Also we talked about natural selection, which this article states, that natural selection might be the reason that we have different races. The article says that we have different races because the hominids that were left from the dispersal evolved into modern humans. Also the article talks about the Out of Africa Model, the model suggests that when Homo erectus left, the hominids that were left may have went through sympatric speciation, which caused Homo sapiens that evolve and were left there breed in other places.
What I found interesting is that Homo erectus and then Homo sapiens left Africa. I wonder why they decided to leave, was because of geographic changes or diet changes. I guess we may never know why they left Africa. Also I wonder how we (modern humans) would look like if Homo erectus and Homo sapiens would have not left Africa. I found it interesting that all existence of the Human species came from Africa. I wonder why evolution chose Africa for the place for human life to start.
We discussed allopatric speciation in class, which is the geographical isolation of a species. In the Multiregional Continuity Model, humans didn't go through speciation since their ranges weren't far enough away and gene flow still occured. This means they stayed close enough relate that they could still mate, which led to why we all have one species and not different species of humans. The out of Africa Model talks about reproductive isoltion and speciation being successful. We discussed in class how if successful speciation does occur that interbreeding can no longer happen between the animals and they are now separate species. What happened then is that Homo Sapiens evolved in one of the groups, spread and conquered, killing off the other species only leaving one, us.
One thing I find interesting is how much Neanderthals changed, due to natural selection. It is a perfect example of adaptation at work. They completely adapted to their cold, harsh climate and were able to successfully survive. I also find it fascinating that even though Homo sapiens and Neanderthals were so anatomically different, they were a lot alike. They were on seperate parts of the Earth but had tools that looked the same, barried the dead and acts some what the same way, at first. Then H. sapiens gained their intelligence and it was all over.
Concepts we talked about in class and are related to this article is gene flow and speciation. The Multiregional Continuity Model is the idea that regional hominid populations slowly evolved into modern humans. The reason speciation did not occur though was due to gene flow still going on. Where as with the Out of Africa Model species were isolated to the point where there was no gene flow. This led to the formation of new species like Homo neanderthalensis and so on. Then later on Homo sapiens went on to replace all of these human species.
Something that interested me in the article probably has to be the hybrid they had found. Especially since it was diffrent from any other hybrid whereas it had the head of a Homo sapien but the body of a neanderthalensis when it should have a mix of many traits through out it's body. I also found it interesting that we did not evolve from neanderthals, but instead shared a common ancestor with them.
@Colleen:
I can only imagine that at the time, Africa may have possessed favorable conditions for sustaining life. It wouldn’t make much sense to start our development in an environment with little food, water, shelter, etc. Evolution could have placed us anywhere I guess; we just would’ve had different traits and whatnot, I assume. I support your questioning as to why our ancestors might’ve left Africa. My only thought to support it would be that they were running short on some crucial resources and needed to find more. The gene flow of modern humans worked well in the sense that it lead up to this, so I don’t have much to argue about it.You did talk about natural selection, too. The development of different races is the most obvious, noticeable result. Going further, one might notice that each of the races has specific traits.
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