Posted on 01/12/2005 8:00:35 AM PST by PatrickHenry
Genes that control the size and complexity of the brain have undergone much more rapid evolution in humans than in non-human primates or other mammals, according to a new study by Howard Hughes Medical Institute researchers.
The accelerated evolution of these genes in the human lineage was apparently driven by strong selection. In the ancestors of humans, having bigger and more complex brains appears to have carried a particularly large advantage, much more so than for other mammals. These traits allowed individuals with “better brains” to leave behind more descendants. As a result, genetic mutations that produced bigger and more complex brains spread in the population very quickly. This led ultimately to a dramatic “speeding up” of evolution in genes controlling brain size and complexity.
“People in many fields, including evolutionary biology, anthropology and sociology, have long debated whether the evolution of the human brain was a special event,” said senior author Bruce Lahn of the Howard Hughes Medical Institute at the University of Chicago. “I believe that our study settles this question by showing that it was.”
Lahn and his colleagues reported their data in a research article published in the December 29, 2004, issue of the journal Cell.
The researchers focused their study on 214 brain-related genes, that is, genes involved in controlling brain development and function. They examined how the DNA sequences of these genes changed over evolutionary time in four species: humans, macaque monkeys, rats, and mice. Humans and macaques shared a common ancestor 20-25 million years ago, whereas rats and mice are separated by 16-23 million years of evolution. All four species shared a common ancestor about 80 million years ago.
Humans have extraordinarily large and complex brains, even when compared with macaques and other non-human primates. The human brain is several times larger than that of the macaque — even after correcting for body size — and “it is far more complicated in terms of structure,” said Lahn.
For each gene, Lahn and his colleagues counted the number of changes in the DNA sequence that altered the protein produced by the gene. They then obtained the rate of evolution for that gene by scaling the number of DNA changes to the amount of evolutionary time taken to make those changes.
By this measure, brain-related genes evolved much faster in humans and macaques than in mice and rats. In addition, the rate of evolution has been far greater in the lineage leading to humans than in the lineage leading to macaques.
This accelerated rate of evolution is consistent with the presence of selective forces in the human lineage that strongly favored larger and more complex brains. “The human lineage appears to have been subjected to very different selective regimes compared to most other lineages,” said Lahn. “Selection for greater intelligence and hence larger and more complex brains is far more intense during human evolution than during the evolution of other mammals.”
To further examine the role of selection in the evolution of brain-related genes, Lahn and his colleagues divided these genes into two groups. One group contained genes involved in the development of the brain during embryonic, fetal and infancy stages. The other group consisted of genes involved in “housekeeping” functions of the brain necessary for neural cells to live and function. If intensified selection indeed drove the dramatic changes in the size and organization of the brain, the developmental genes would be expected to change faster than the housekeeping genes during human evolution. Sure enough, Lahn's group found that the developmental genes showed much higher rates of change than the housekeeping genes.
In addition to uncovering the overall trend that brain-related genes — particularly those involved in brain development — evolved significantly faster in the human lineage, the study also uncovered two dozen “outlier” genes that might have made important contributions to the evolution of the human brain. These outlier genes were identified by virtue of the fact that their rate of change is especially accelerated in the human lineage, far more so than the other genes examined in the study. Strikingly, most of these outlier genes are involved in controlling either the overall size or the behavioral output of the brain — aspects of the brain that have changed the most during human evolution.
According to graduate student Eric Vallender, a coauthor of the article, it is entirely possible by chance that that two or three of these outlier genes might be involved in controlling brain size or behavior. “But we see a lot more than a couple — more like 17 out of the two dozen outliers,” he said. Thus, according to Lahn, genes controlling the overall size and behavioral output of the brain are perhaps places of the genome where nature has done the most amount of tinkering in the process of creating the powerful brain that humans possess today.
There is “no question” that Lahn's group has uncovered evidence of selection, said Ajit Varki of the University of California, San Diego. Furthermore, by choosing to look at specific genes, Lahn and his colleagues have demonstrated “that the candidate gene approach is alive and well,” said Varki. “They have found lots of interesting things.”
One of the study's major surprises is the relatively large number of genes that have contributed to human brain evolution. “For a long time, people have debated about the genetic underpinning of human brain evolution,” said Lahn. “Is it a few mutations in a few genes, a lot of mutations in a few genes, or a lot of mutations in a lot of genes? The answer appears to be a lot of mutations in a lot of genes. We've done a rough calculation that the evolution of the human brain probably involves hundreds if not thousands of mutations in perhaps hundreds or thousands of genes — and even that is a conservative estimate.”
It is nothing short of spectacular that so many mutations in so many genes were acquired during the mere 20-25 million years of time in the evolutionary lineage leading to humans, according to Lahn. This means that selection has worked “extra-hard” during human evolution to create the powerful brain that exists in humans.
Varki points out that several major events in recent human evolution may reflect the action of strong selective forces, including the appearance of the genus Homo about 2 million years ago, a major expansion of the brain beginning about a half million years ago, and the appearance of anatomically modern humans about 150,000 years ago. "It's clear that human evolution did not occur in one fell swoop," he said, "which makes sense, given that the brain is such a complex organ."
Lahn further speculated that the strong selection for better brains may still be ongoing in the present-day human populations. Why the human lineage experienced such intensified selection for better brains but not other species is an open question. Lahn believes that answers to this important question will come not just from the biological sciences but from the social sciences as well. It is perhaps the complex social structures and cultural behaviors unique in human ancestors that fueled the rapid evolution of the brain.
“This paper is going to open up lots of discussion,” Lahn said. “We have to start thinking about how social structures and cultural behaviors in the lineage leading to humans differed from that in other lineages, and how such differences have powered human evolution in a unique manner. To me, that is the most exciting part of this paper.”
humanists would be dumbstruck without their "special events," wouldn't they?
I honestly don't think any of you have *really* read Genesis. Read just the first 3 chapters and tell me that it's compatible with evolution. Note the words "kind," note that Adam was formed from dust first, and then Eve was created from his rib. Note that the grass was created before the sun. How does :rested on the seventh day" compatible with evolution? Genesis 2:6 talks about how foliage was watered (not by rain, by the way). Where did Noah's Flood come from? And so on....
>>Why do you correlate smartness with feebleness?<<
I don't. I just like to exploit stereotypes. 8^>
Funny thing is, though, that most people are endowed pretty much equally. That is, A guy whos brain is extremely adept at hand eye coordination (gifted three point shooter) is usually less so in the study of fluid dynamics.
The converse tends to be true as well.
Another truth I have observed, especially in women, is that the more beautifull they are (universally accepted), the less they have had to depend on attributes other than their physical appearance to get what they want in life. I am talking "natural" beauty here, not plastic surgery and silicone, which weren't available back "in the day."
Oh, and neither were Zig Ziegler or Brian Tracy.
The parents of cave kids weren't particularly adept at the higher concepts of long term goal setting and motivational teaching - it was about getting what you want and, at it's core, survival.
It was not until the last hundred years or so that raw survival was not first and formost in the minds of most human beings that inhabited this planet. It is still first and formost for most, come to think about it.
But you gotta love that comment about evolution working "extra hard," heh, heh.
Funny you should mention viruses.
Native Americans had no defense against viruses unlike the Europeans who had been struggling with them for some time and had evolved resistances. Viruses wiped out entire tribes, leaving the Europeans with strength of numbers and allowing them to take over easier. In other words, a form of natural selection.
Scripture has God creating the sun, moon, and stars the day *after* he created the grass and trees. It takes a lot of faith to believe Scripture, but if you do believe it, then it's laughably incompatible with evolution.
Another thing is this "firmament." Evolution doesn't talk about a water canopy (which seems to have fallen during the Great Flood), but Scripture does.
The more you study the first few chapters of Genesis, the more it's laughably different from standard theories of evolution. You need to laugh at either the Scriptural account, or the Evolutinists' account.
This is also treating speciation as a black/white issue. One prediction that evolution makes is that there should be cases where it is difficult to determine if a new species has formed or not. For example, are chihuahuas and great danes the same species? One widely used definition of species is that two organisms are the same species if they can successfully interbreed. Can a female chihuahua really successfully mate with a male great dane? Can it successfully give birth to great dane/chihuahua hybrid pups? It is questionable as to whether this could occur or not. It also points out another weakness of this definition of species, namely that the ability to interbreed is not a transitive property. That is given that organism A can interbreed with organism B and that organism B can interbreed with organism C, it is not strictly true that organism A can necessarily interbreed with organism C. (think of A=chihuahua, B=some medium sized breed of dog, C=great dane) Would organisms A and C be the same species or different ones? Going strictly by the successful interbreeding definition, they are not. There are several examples of this phenomenon, and it is exactly what we would expect if evolution is the mechanism that produces new species.
I don't think such things correlate at all. A gifted 3-point shooter is exactly as likely as anyone else in the population to be gifted at fluid dynamics too (though he may get less chance to show it and have less reason to work his academic skills up to their potential because of the marketability of his ball skills)
Some of the smartest people I've ever met were also good athletes.
That is one of the errors that will be eliminated once laws requiring textbook accuracy are eliminated. It has been discovered, much to the embarrassment of evolutionists, that the moths are nocturnal and are not found on tree trunks during the day. They were glued there for a faked photo. But even if it were not faked, evolutionists have conceded it is not evidence for evolution.
Also, the fossil record shows many examples of evolution. Species appear and disappear in the fossil record throughout time. The Creation story doesn't explain that.
The flood explains the fossil record better than evolution. Evolution expects the record to show gradual change over time with intermediate forms. Creation predicts fully formed organisms and no intermediate forms. The flood would leave mass graves of rapidly buried and often disarticulated organisms. Evolution has no adequate mechanism for explaining the mass graves. Creation would anticipate polystrate fossils. Evolution is at a loss. Creation does not have "out of place artifacts". They are a constant problem for uniformitarians.
Decades ago I was an evolutionist like you. My biggest objection to special creation was the supposed fossil men. Upon closer investigation it became apparent that the missing link is still missing. Of course you will be told that there aren't any missing links, as my anthropology teacher insisted, yet there isn't any evidence stronger than speculation to support the evolution of man. If there were, evolution would be a fact and have public support, which it isn't and doesn't.
If evolution were true, the textbooks wouldn't need to promote the peppered moth hoax. If evolution were true, evolutionists wouldn't need to fabricate evidence to support it.
Since according to the theory of evolution, natural selection requires millenia to perform its magic, then I would say the point is moot since neither I nor you will be around on this earth to believe anything at that point. :)
While I believe that it is "possible" that God created the earth through the process of evolution, like someone already said, it's hard to imagine God creating a human being like Adam that way.
If you study creation science, all of the "proof" of evolution actually has been responded to and debunked.
I am not an expert on the subject myself, but there are books that go into the many points of evolution and offer a creation response.
One specifically I remember is that carbon dating, which is used to back up the idea that the earth is billions of years old, has also been used on articles of which the specific age is known. The carbon dating method gave results that were false.
Creation Science explains that carbon dating works by determining the amount of carbon in the item. This does not take into acount the fact that most things arleady contain carbon.
Another evidence used to back up evolution, is the layers of earth and the fossils found in those layers. However, if you believe in the Biblical account of the flood, those layers are also easily explained.
There is also signifigant lack of a fossil trail from ape to man (the so-called missing link). It's hard to imagine that if evolution were true, at least one of these inbetween creatures about to evolve into a human being would not have been found.
The fossil trail that has been found is believed to have been created from parts of different creatures.
A little research and an open mind and study of creation science may change your mind.
I'm not arguing that women choose men by their IQ. I'm saying they prefer men who are wealthy and powerful. Wealth and power are going to correlate with brainpower, even if their are exceptions.
The capacity to survive the total annihilation of the planet is only an evolutionary advantage if the planet is actually totally anihilated. Barring this, those species that are most successful at reproducing, given their actual environment are the ones that are the "pinnacle of evolution." By that measure, the sauropods were very successful until their environment changed radically. It is easy to imagine an environment in which humans would not be particularly successful. For example, if tommorrow a full blown nuclear war were to start, with nuclear detonations occurring over the majority of land masses of the earth, it would be the cockroaches, not humans, that prove to be the most successful species, since humans aren't particularly well suited to environments with high levels of radioactivity. (not to mention that it would be humans themselves who caused the environmental change that leads to their demise, not the hallmark of an extremely successful species.) Furthermore, in terms of evolutionary success, it isn't humans that are the most successful organisms. I can think of at least two groups of organisms (insects and bacteria) that are much more successful than huamns in terms of their ability to propogate the species.
If you believe this, and you want to believe the bible, then you are setting yourself up for a lot of mockery. A strict literal interpretation of the early chapters of Genesis doesn't stand up to any kind of critical scrutiny.
So is it more about money and power or intelligence? I always thought the physical aspect was important, you know, big, healthy strong men were more desirable to try to produce healthy offspring.
Thanks for the ping!
Yeah, 'cause us modern types are still confounded by ol' Xeno's arrow...
I think women are wired to find successful men attractive. Success in a hunter-gatherer society might mean a smart, strong hunter who is capable of bringing home the mammoth. Success in today's society might mean a lawyer or doctor.
You and I think a lot alike. I was astounded when I was in my early 20s to *really learn* about creation as described in Genesis and as further illustrated by creation scientists. Amazing how cohesive it is once you shed your prejudice against it.
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