Topic: Distant Ancestors

[Josh]

[Jahn]

Talking evolution, can someone tell me why not all evolve. I mean why are there still monkeys, dogs, raccoons, birds and bees etc?

That monkey should have transformed ages ago to something more refined kind of logic.

May sound stupid to ask but if we really shall go mental this is a good question: why simply do not everyone in each spiecies transform. Sharks, alligators and the like know to be some really original inhabitants on this earth. It isn't necessary to transform for their survival, food supply or what? Why was it then necessary for the other of the same species. Suppose I slept thru biology.

[nichi]

Lemurs!   

[nichi]

Talking evolution, can someone tell me why not all evolve. I mean why are there still monkeys, dogs, raccoons, birds and bees etc?

Because we need diversity?

[Jahn]

Because we need diversity?

I can't imagine that "we" have anything to do with that, maybe nature need and want diversity -  that seems logical to me.

How does a transformation from one phase to another looks like is another question I have. I mean we can see a change when different dogs mix or a horse and a donkey but I would not call that evolution, only effects mixing.

[Jahn]

Aum, mani padme hum
Aum, peace peace peace

[nichi]

I can't imagine that "we" have anything to do with that, maybe nature need and want diversity -  that seems logical to me.

Oh sorry -- by "we" I meant Life, not just the little subset of humans!
"We" the whole -- the ecosystem -- need everything therein. 

[erik]

One thing is the evolution of biological vehicles for incarnation of mind.
The other thing is incarnation of mind in various vehicles for purposes of evolution.

I'd guess the reason is twofold there - to have sufficiently stable, but gradually evolving ecosystem you need many slowly evolving species.

To have evolution of mind, you need various biological vehicles at different stages of evolution.

See the difference:

[nichi]

How does a transformation from one phase to another looks like is another question I have. I mean we can see a change when different dogs mix or a horse and a donkey but I would not call that evolution, only effects mixing.

Maybe evolution is "effects mixing" over eons -- I don't know!
I'm not a strict evolutionist, myself. There are huge pieces to that puzzle which we are missing, knowledge-wise, imho.

The reasons for the missing pieces probably go to the feature of the concept which is linear. It always seemed 'forced' to me to put the "history of life" into a line of "lesser to better".  Some would say that in the end, it was a theory of its time, created in order to justify the "superiority" of the imperialists. If they were "superior", then they somehow had the "right" to conquer and exploit.

Was Darwin a product of his time, in other words?
   

[Josh]

The researchers, led by Bruce Lahn, Assistant Professor in Human Genetics, presented evidence that the pressure of natural selection has led to dramatic evolutionary changes in a gene called Microcephalin and another gene called ASPM. Both are known to control brain size during development in humans. Patrick Evans, Jeffrey Anderson, Eric Vallender, Sandra Gilbert, Christine Malcom, Steve Dorus and Sun Shim Choi, all seven of whom work in Lahn’s laboratory, were co-authors of the paper.

“People have studied the evolution of the brain for a long time, but they have traditionally focused on the comparative anatomy and physiology of brain evolution,” said Lahn, who also is an Assistant Investigator in the Howard Hughes Medical Institute. “I would venture, however, that there really hasn’t been any convincing evidence until now of any gene whose changes might have contributed to the evolution of the brain.”

The researchers decided to explore Microcephalin and ASPM because mutant forms of these genes cause primary microcephaly, a developmental defect that affects humans. This disorder is marked by a severe reduction in the size of the brain, particularly the cerebral cortex—the part of the brain responsible for planning, abstract reasoning and other higher brain functions. The brains of people with primary microcephaly are otherwise normal, and other structures of the body seem unaffected.

The researchers traced the evolution of Microcephalin and ASPM by comparing the genes’ sequences in a range of primates, including humans, as well as non-primate mammals. Specifically, the researchers sequenced the human, chimpanzee, gorilla, orangutan, gibbon, colobus monkey, squirrel monkey and lemur forms of the genes.

“We chose these species because they were progressively more closely related to humans,” said Lahn. “For example, the closest relatives to humans are chimpanzees, the next closest are gorillas, and the rest go down the ladder to the most primitive.”

The sequence of primates from human to lemur generally represents a progression from the most advanced to the more primitive. Chimpanzees are the closest, living genetic relative of humans, and the lemur represents the most primitive primate, having branched from the primate tree before the evolution of monkeys, apes and humans. To study the evolution of the genes in other mammals, the researchers also sequenced these genes from the dog, cat, cow, sheep, rat and mouse.

For each species, the researchers identified changes in both the Microcephalin and the ASPM genes that altered the structure of the resulting proteins, as well as those that did not affect protein structure. Only those genetic changes that alter protein structure are likely to be subject to evolutionary pressure, Lahn said. Changes in the gene that do not alter the protein indicate the overall mutation rate—the background of random mutations from which evolutionary changes arise. Thus, the ratio of the two types of changes gives a measure of the evolution of the gene under the pressure of natural selection.

“We were a bit surprised that, when we went from ASPM to Microcephalin, we saw a very similar pattern repeating itself, although not exactly the same,” said Lahn. “That is, we saw an acceleration in the evolution of the protein sequence throughout the lineage from simian ancestors to humans and chimpanzees.” However, said Lahn, while changes in the ASPM gene showed the most dramatic acceleration in the later lineage from ape ancestors to humans, the greatest acceleration in the evolution of the Microcephalin gene occurred early in the primate lineage.

“This provides strong evidence that the evolution of the Microcephalin gene is highly accelerated, specifically along the lineage leading to humans, but not necessarily in a terminal human branch,” said Lahn. “Acceleration has actually been more intense in the early part of this lineage—going from simian ancestors to apes.”

The researchers concluded that this difference could mean that Microcephalin was more involved in the earlier stages of evolution of primate brain size, while ASPM might have contributed more to brain expansion closer to the final evolutionary step to humans.

The researchers also compared the subtle variations in the Microcephalin and ASPM genes among humans, and found further evidence of an evolutionary pressure driving the changes in these genes.

Although the studies are preliminary, said Lahn, the evidence of evolutionary pressure on the two genes offers a hint at the basic mechanism by which the large human brain evolved. “Two genes don’t really make a trend,” he said. “But they certainly make it a tantalizing hypothesis that genes that control brain size or gross morphology during development will be disproportionately involved in brain evolution.”

The researchers are continuing their studies to determine the biological function of the two genes, to better understand how their mutation could have led to the characteristic enlargement of the human brain.

“We want to know when was the last time that the lightning of evolution struck either one of these genes during human evolution,” said Lahn. “Was it 100,000 years ago, or a million years ago or half a million years ago? That would be fascinating to know from the viewpoint of understanding the history of evolution of the human brain.”

[Jahn]

Interesting stuff, even if it doesn't explain it all. It takes two to tango. It is no use if one animal evolves or mutates in a herd, to make the new DNA to survive it needs a partner, a mix with the old would risk to take away the progress.

However in the article it is mentioned a kind of probability for mutations. I think we got the answer there. The equation generate a ceratin number of mutants but the vast majority is unaffected. 

"Changes in the gene that do not alter the protein indicate the overall mutation rate—the background of random mutations from which evolutionary changes arise. Thus, the ratio of the two types of changes gives a measure of the evolution of the gene under the pressure of natural selection."