Beginning of Human Evolution (Divergence from other Apes)
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10-08-2012, 02:01 PM
Beginning of Human Evolution (Divergence from other Apes)
The chimpanzees, monkeys, gorillas, etc. are fairly similar to one another, as opposed to humans. Why are they like this? Considering that humans have 46 instead of 48 chromosomes like the aforementioned, I would assume that the chromosome fusion had something to do with it. Is this how humanity started? A genetic aberration that rendered some individuals incapable of breeding with the population before? But if so, then how did humanity begin to prosper? Are all the "other" humans, now extinct, derived from the same fusion, or are these separate instances?

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10-08-2012, 03:18 PM
RE: Beginning of Human Evolution (Divergence from other Apes)
(10-08-2012 02:01 PM)nsguy1350 Wrote:  The chimpanzees, monkeys, gorillas, etc. are fairly similar to one another, as opposed to humans. Why are they like this? Considering that humans have 46 instead of 48 chromosomes like the aforementioned, I would assume that the chromosome fusion had something to do with it. Is this how humanity started? A genetic aberration that rendered some individuals incapable of breeding with the population before? But if so, then how did humanity begin to prosper? Are all the "other" humans, now extinct, derived from the same fusion, or are these separate instances?

Chimps are more like humans than they are like other apes. And, yes, we have a fused chromosome that makes us reproductively isolated from chimps.

Unless we can get DNA from earlier hominin species, we won't be able to answer detailed genetic questions.

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10-08-2012, 03:35 PM (This post was last modified: 10-08-2012 03:38 PM by kim.)
RE: Beginning of Human Evolution (Divergence from other Apes)
(10-08-2012 02:01 PM)nsguy1350 Wrote:  The chimpanzees, monkeys, gorillas, etc. are fairly similar to one another, as opposed to humans. Why are they like this? Considering that humans have 46 instead of 48 chromosomes like the aforementioned, I would assume that the chromosome fusion had something to do with it. Is this how humanity started? A genetic aberration that rendered some individuals incapable of breeding with the population before? But if so, then how did humanity begin to prosper? Are all the "other" humans, now extinct, derived from the same fusion, or are these separate instances?

All members of the great ape primates except humans have 24 pairs of chromosomes. Humans have only 23 pairs of chromosomes. There's a particular chromosome which humans have called chromosome 2. To get this chromosome 2, certain things have to happen and keep happening AND it has to keep happening in different groups. Chromosome 2 is widely accepted to be a result of an end-to-end fusion of two ancestral chromosomes. This is very strong evidence which would point to the common descent of humans and other apes.

I would think that these "transitional" humans were pretty busy socializing amongst themselves and there is little evidence of mingling. Recent excavations in Israel, Portugal, and Croatia show clearly that Neanderthals were contemporary with modern Homo sapiens sapiens. The two hominids apparently survived independently of each other for tens of thousands of years.

Go Caveman! Wink

Interesting link about dead guys.

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10-08-2012, 03:49 PM (This post was last modified: 10-08-2012 03:53 PM by ghostexorcist.)
RE: Beginning of Human Evolution (Divergence from other Apes)
It is important to remember that chimps and bonobos are more closely related to humans than they are to gorillas, orangutans, and, especially, gibbons. They share nearly 99% of our DNA. This means that there is only roughly a 1% difference between us. However, all of our differences in morphology and cognitive abilities are contained within the 1%.

Regarding the fusion of human chromosome 2, Carl Zimmer explains: "Every now and then, chromosomes fuse. This fusion occurs as sperm and eggs develop, as pairs of chromosomes fold over each other and swap chunks of DNA. Sometimes two different chromosomes grab onto each other and then fail to separate.” He goes on to say that the ends of chromosomes are prone to duplication errors and fusions. Sometimes a chromosome will duplicate and flip parts of itself inward, or they will grab onto parts of the ends of other chromosomes. These errors happened to the chromosomes of the joint human-chimp-gorilla ancestor. These errors were inherited by the joint human-chimp ancestor after it split from gorillas. After the human and chimp lines split, the chimps experienced their own errors, which were later capped with new pieces of DNA and became species specific. Humans continued to have their own errors, which resulted in the complete fusion of chromosome 2. The fusion mended the ends prone to errors, making it specific to our species. See here for a far more eloquent explanation and diagrams.

I’ve read that the fusion may have boosted our cognitive abilities. Chimps are already very intelligent creatures, even more so than humans born with mental handicaps. They use stone tools, coordinate hunts, are excellent problem solvers—they are notorious for picking locks in zoos—and are able to successfully navigate the highly complex social structure of chimp society. The joint human-chimp ancestor was presumably this smart. Now, just imagine what an added survival advantage increased intelligence would have been for the human lineage. Each species of human would have inherited this.

I don't think the fusion resulted in the morphological differences between humans and chimps. The human body is the result of 7 million years of independent evolution from our ape cousins. We left the trees and spent more time on the savannahs, which changed our means of locomotion. Chimps can walk on their feet, but only for a short time. They put most of their weight onto their padded knuckles. We most likely switched to bipedal locomotion because it requires less energy than walking on all fours and because we needed our hands to carry food or tools over flat ground. An upright posture also provides less surface area for the sun to heat up. Likewise, we lost our hair to cool us off. This resulted in the darkening of our skin via melanin. (Humans who later moved to rainy or snowy climates outside of Africa needed lighter skin to absorb more vitamin D.) Our facial structure and jawline changed due to a mutation and or change in diet. We were no longer eating hard nuts, tree bark, and raw meat filled with bones, so we didn’t need powerful jaws anymore. Of course our brain pans responded to the growth of our brains via adaptation to the changing environment of Africa and eating cooked meat. The gracilization of our skeletons was probably brought on by sexual selection and the adoption of egalitarian societies (see this post here).
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10-08-2012, 04:09 PM
RE: Beginning of Human Evolution (Divergence from other Apes)
That's just looking at it with a selective human bias.

If a monkey had the mental ability to do such a thing.. It could very well look at Great Apes, or just Chimps and Humans saying, how come they are so much alike in: this, that, or whatever way in which we are?

"Allow there to be a spectrum in all that you see" - Neil Degrasse Tyson
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10-08-2012, 04:32 PM
RE: Beginning of Human Evolution (Divergence from other Apes)
(10-08-2012 04:09 PM)ClydeLee Wrote:  That's just looking at it with a selective human bias.

If a monkey had the mental ability to do such a thing.. It could very well look at Great Apes, or just Chimps and Humans saying, how come they are so much alike in: this, that, or whatever way in which we are?

No, it's looking at it genetically.

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10-08-2012, 06:16 PM
RE: Beginning of Human Evolution (Divergence from other Apes)
Excellent. Wow. A few days ago, I was staying after class with some people. One woman (I was attending a community college, although I am a high school student. Took one class I needed for credit there.) said her speech was on creationism/evolution. I asked her what side she was on, and she said creationists.

I tried to hold it in for a while, but then we got into a discussion. She asked me how humans got here, and I told her about speciation, and talked about the fusion of chromosomes. I wasn't sure, I kinda inferenced, but now that I have confirmation, great!! Thanks guys. I didn't know chimps were so smart!

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I am glad to live where there is no God, for I am moral, and mortal; I do not wish to worship He who crafts an immoral immortality.
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11-08-2012, 01:26 AM
RE: Beginning of Human Evolution (Divergence from other Apes)
I would be cautious about assuming that the chromosome fusion had any really significant morphological effect. It might have been associated with actual gene changes, but not necessarily.

It's probably best to think of chromosomes as magnetic tape. They contain the genes that are expressed to make up an individual's heredity but unless a particular gene is broken or changed it doesn't necessarily have any impact to cut and splice to tape itself. A chromosome is a DNA molecule, but most of the information does not code for specific proteins. Only the genes, the "files" on this magnetic tape really impact morphology.

So in theory it is possible to:
* Splice two chromosomes together
* Split a chromosome in to two
* Move or copy a gene from one chromosome to another
All without making any change to the set of genes that make up an individual - without imposing any positive or negative effects.

Changes to the genes include things like:
* Deleting or inserting a base pair, causing the rest of the gene to become a completely new gene.
* Changing a base pair within a gene
* Enabling or disabling a gene
* Various others
Many of these changes are only possible after a gene has been duplicated so that the original gene function is not lost.

Give me your argument in the form of a published paper, and then we can start to talk.
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11-08-2012, 03:49 PM
RE: Beginning of Human Evolution (Divergence from other Apes)
(10-08-2012 03:49 PM)ghostexorcist Wrote:  These errors happened to the chromosomes of the joint human-chimp-gorilla ancestor. These errors were inherited by the joint human-chimp ancestor after it split from gorillas. After the human and chimp lines split, the chimps experienced their own errors, which were later capped with new pieces of DNA and became species specific. Humans continued to have their own errors, which resulted in the complete fusion of chromosome 2. The fusion mended the ends prone to errors, making it specific to our species.

Oh man... that right there... I had me a little mind-gasm. Blush

Thanks. Wink

I think in the end, I just feel like I'm a secular person who has a skeptical eye toward any extraordinary claim, carefully examining any extraordinary evidence before jumping to conclusions. ~ Eric ~ My friend ... who figured it out.
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12-08-2012, 11:52 AM
RE: Beginning of Human Evolution (Divergence from other Apes)
(11-08-2012 03:49 PM)kim Wrote:  Oh man... that right there... I had me a little mind-gasm. Blush

Thanks. Wink

I'm glad you liked it. I can't take credit, though. Genetics is still a weak subject for me. The Carl Zimmer article that I linked above helped me to grasp what happened in our lineage.
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