Are genes related to brain development different between humans and chimps, yes or no? When that answer is yes, that means that there are genetic variants that can result in higher levels of intelligence by default.
Those differences are divergence and by their very nature demand a burden of proof, not just to the effect but the cause. Mutations are the worst possible explanation. We know many things about the effects of mutations on brain related genes and random copy errors don't result in bigger and better brains, they result in disease and disorder. Your not going to get around that one.
The variation in species, and the subtle to extreme differences they afford, make every living thing on this planet inherently contradict your claim that no mutation or group of mutations could have a significant beneficial impact on intelligence.
That's the problem, the equivocation of variation with mutations. I'm well aware that genes are sometimes modified, sometimes by still unknown molecular mechanisms. My point is simply that mutations in brain related genes yield disease and disorder like cancer, tumors, Fragile X syndrome and a host of neurological disorders.
We can literally quantify many of the genetic differences between humans and other species that makes us more intelligent than they are. Heck, what do you make of a genus born to parents with average intelligence, hmm? The variation within our own species in terms of intelligence defeats your claim that mutations can never benefit intelligence.
So why don't we have examples? Mutations in brain related genes on an evolutionary scale effecting brain related genes. The brain of the hominids has to nearly triple in size and we are learning that this is directly linked to more then gene expression, brain related genes have to be profoundly changed. Mutations, is the worst possible example of a possible cause due to functional constraints and especially the known deleterious effects.
We just give more attention to the mutations that do bad than those that do good. What about the mutation in an extended family in Italy that makes them practically immune to cholesterol build up and heart disease? A member of that family in her 70s had the arteries of someone in their 20s. Is that not beneficial to you?
That's a great example, a little less specific then I like but perfectly applicable. I know that adaptive evolution happens with regards to cholesterol and brain related genes are different things. Surely you see this.
Yes, so why couldn't this satisfy you claim for the degree of physical difference needed to produce higher intelligence? Slight changes in the genetic code can have drastic consequences, and they aren't inherently negative.
There is an evident and obvious reason why this is a problem, call it skepticism if you will. They are either deleterious in their effects or do nothing at all. I'm talking about HAR1f and other vitally important genes changing over night about two million years ago. The question has to be, how. If you say mutations your obviously wrong.
-_- what do you think would have caused the amino acid substitution to run in families aside from genetic mutation? It can't just be environment, because not everyone with this trait lives similarly.
It's anecdotal, that's the problem.
Definitions of metaphysics:
the branch of philosophy that deals with the first principles of things, including abstract concepts such as being, knowing, substance, cause, identity, time, and space.
- abstract theory or talk with no basis in reality.
The first cause of life has no basis in reality? Is that really your argument in a topic related to the ongoing controversy between evolution and creation? Science isn't allowed to make an inference with regards to a miracle but that doesn't mean there is no such thing in reality, especially with regards to the origin of life.
The theory of evolution was derived originally by observations Darwin made about wildlife, that is its initial basis in reality. We observe changes in the trends of traits in populations over time, that is the basis. If a mountain has consistently grown 4 inches taller every year for the past 40 years, is it truly inconceivable to conclude that the year prior to the first measured year, it probably grew 4 inches?
So we go from Charles Darwin making inference about Orchids and pigeons to the development of the human brain from that of apes? Really? Then we are going to somehow relate that to mountains. Things changing and things changing on a massive scale are obviously two different things, certainly geology and biology are two different things.
A bigger, better brain could be the result of just one mutation, you know. The genes for human brain development and for, say, the brain development of a mouse, are almost exactly the same.
That's just not true:
Bruce Lahn, the senior author at the Howard Hughes Medical Center at the University of Chicago and colleagues have suggested that there are specific genes that control the size of the human brain. These genes continue to play a role in brain evolution, implying that the brain is continuing to evolve. The study began with the researchers assessing 214 genes that are involved in brain development. These genes were obtained from humans, macaques, rats and mice. Lahn and the other researchers noted points in the DNA sequences that caused protein alterations. These DNA changes were then scaled to the evolutionary time that it took for those changes to occur. The data showed the genes in the human brain evolved much faster than those of the other species. Once this genomic evidence was acquired, Lahn and his team decided to find the specific gene or genes that allowed for or even controlled this rapid evolution. Two genes were found to control the size of the human brain as it develops. (
Evolution of the brain Wikipedia)
Much more similar between humans and other apes. And other apes aren't stupid, if you speak sign language, you can have conversations with them, they're about as smart as 4-8 year old human children. Structurally, the brain of a chimp is almost exactly like a smaller version of a human brain. It doesn't take many mutations to change the size of an organ. Consider this scenario: what if the norm in the past was a genotype that would be associated with mental defect in our species today, and what was a rare mutation in the past is what the modern common genotype is derived from?
Are you really sure about that?
FIGURE 2. Comparative neuroanatomy of humans and chimpanzees. (Genetics and the making of Homo sapiens. Nature April 2003)
Doesn't need to be many for evolution to act upon.
Darwin discussed what he called the 'bane of horticulture', this was infertility. Haldane in 'The Cost of Natural Selection indicated "genetic deaths," which is either deaths or it's equivalents in reduced fertility. He said that it would take 300 generations for a beneficial mutation to become fixed with 1667 accrued in 10 million years.
Like Darwin, he used artificial selection to illustrate what would have had to happen in natural settings:
"especially in slowly breeding animals such as cattle, one cannot cull even half the females, even though only one in a hundred of them combines the various qualities desired." (Haldane, The Cost of Natural Selection)
For us to have evolved from apes it would have required an accelerated evolution of brain related genes. The evolution of the human brain would have had to start it's accelerated evolution on a molecular basis some 2 million years ago and within Homo Erectus (considered human by most creationists) would have had a brain size twice that of the Austropihicene and early Hominids:
Early Ancestors:
A. Afarensis with a cranial capacity of ~430cc lived about 3.5 mya.
A. Africanus with a cranial capacity of ~480cc lived 3.3-2.5 mya.
P. aethiopicus with a cranial capacity of 410cc lived about 2.5 mya.
P. boisei with a cranial capacity of 490-530cc lived between 2.3-1.2 mya.
OH 5 'Zinj" with a cranial capacity of 530cc lived 1.8 mya.
KNM ER 406 with a cranial capacity of 510cc lived 1.7 million years ago.
The evidence is mounting and gene expression isn't an explanation. Mutations is even worse and there is really no clue as to a molecular mechanism.
Shockingly, a lot of the genes associated with brain function are not highly conserved, mostly just the genes that direct the brain to form at all, and where it should go. Why do you think mental disorders are so common in our species? Almost 20% of humanity is mentally defective in one way or another. Here's the thing: as long as it doesn't stop you from reproducing, it can be passed on to the next generation anyways. Also, you say "de novo" as if we don't experience genetic mutations all the time. Every person is born with between 40-60 de novo genes, so why are you acting like 60 is a problem? That's not very many mutations.
Hang on! Every person is born with 40-60 de novo genes? 40 to 60 brand new genes? On average humans across the spectrum diverge by one tenth of one percent and your telling me brand new genes are emerging every generation? That's completely and patently absurd.
-_- mutations are mistakes that life has to deal with. Occassionally, those mistakes result in something good, like how sticky notes and silly putty and puffed chips are the results of errors. Most errors don't result in anything good, that's fine and dandy, the fact that any do gives natural selection something to act on.
The rarest of effects from mutations are beneficial, with the exception of those adaptive on an evolutionary scale.
Furthermore, your own quote hurts your point that "less sleep is one thing, but increased intelligence is another". This is because the deaths that come with producing a drastic change are EQUIVALENT to those producing a minor one. Of the approximately 2 million different egg cells in my body when I was born, how many do you think would even have a chance of becoming a realized human? Well, the world record of births from a single mother that had kids live past infancy is 67 (she gave birth to 69, and two died in infancy). That means the human female with the highest evolutionary fitness only had 0.00335% of her egg cells succeed at most (I highly doubt that every child born as a twin, triplet, and quadruplet was fraternal, so that percentage is likely lower). And let's not even get started on how many sperm cells men produce compared to the number that fertilize eggs. So, there's the necessary deaths for you. Who said they had to happen after fertilization, when sex cells can genetically fail without fertilization?
The diversity of the earliest stages of development, here illustrated strictly within the vertebrates, provides one of the strongest challenges to the neo-Darwinian conception of homology and macroevolution. Given the hierarchical, step-wise logic or "architecture" of animal development, early stages such as cleavage and gastrulation lay the groundwork for all that follows. Body plan structures in the adult, for example, trace their cellular lineage to these early stages. Thus, if macroevolution is going to occur, it must begin in early development. Yet it is precisely here, in early development, that organisms are least tolerant of mutations. Furthermore, the adult homologies shared by these vertebrates commence at remarkably different points (e.g., cleavage patterns). How then did these different starting points evolve from a common ancestor? (
Homology, a Concept in Crisis)
That is the last place you would expect a mutation to have a beneficial effect but that is exactly where it would have to occur. That's not making a lot of sense to me.