quote:Chimpanzees and humans split from a common ancestor just 4 million years ago -- a much shorter time than current estimates of 5 million to 7 million years ago, according to a study published on Friday.
The researchers compared the DNA of chimpanzees, humans and our next-closest ancestor, the gorilla, as well as orangutans.
They used a well-known type of calculation that had not been previously applied to genetics to come up with their own "molecular clock" estimate of when humans became uniquely human.
Just last May, David Reich of the Broad Institute at the Massachusetts Institute of Technology and Harvard Medical School's Department of Genetics found evidence that the split probably took 4 million years to occur, although his team put the final divergence at just 5.4 million years ago.
"I don't think it really contradicts our paper," Reich said in an e-mail exchange.
"We were focusing on a maximum time for the common ancestor of humans and chimpanzees, while they were focusing on a best estimate," added Reich, who reviewed Hobolth's paper before it was published.
From PLoS link:
quote:To estimate speciation times and ancestral population sizes we have developed a new methodology that explicitly utilizes the spatial information in contiguous genome alignments. Furthermore, we have applied this methodology to four long autosomal human-chimp-gorilla-orangutan alignments and estimated a very recent speciation time of human and chimp (around 4 million years) and ancestral population sizes much larger than the present-day human effective population size. We also analyzed X-chromosome sequence data and found that the X chromosome has experienced a different history from that of autosomes, possibly because of selection.
After using a statistical correction for substitution rate heterogeneity, Patterson et al. [2] found that the variance in coalescence times is too large to be accounted for by instant speciation and a large ancestral effective population size, and that the speciation process therefore must have been complex. Particularly, the X chromosome shows a deviant pattern, which also led them to conclude that HC gene flow ceased and final speciation occurred as recently as 4 Myr ago. This date is generally believed to be the most recent time compatible with the fossil record, if the Millennium man and Sahelanthropus are not on the human lineage.
That would put australopithicus very close to the split.
This is still a mathematical model of split time based on some kind of uniform rates of mutation ... or at best an average rate.
I'm not sure that such models are valid for periods of speciation, when there can be more impetus for divergence to reduce direct competition.
Just how well established is the model for a 'genetic clock' for mutations to begin with?
The problem is: how do you baseline it?
You can measure current rates of mutation and then assume that the rate stays constant (we wouldn't have a baseline long enough to do otherwise), but then you need some kind of measure of how many get fixed in the population - that's going to be another estimate (one I have some trouble with as we know that selection pressure can change this), and it is also going to be some rather uniform or average rate (due to lack of model for rate change or data to base one on that is more than a few years long).
What they apparently did on this study was to use an 'accepted' age of the orangutan split as a baseline:
quote:The researchers compared the DNA of chimpanzees, humans and our next-closest ancestor, the gorilla, as well as orangutans.
"Assuming orangutan divergence 18 million years ago, speciation time of human and chimpanzee is consistently around 4 million years ago,"
So this is based on an average rate of mutation fixing in the orangutan line applied to the gorilla-chimp-human lineage.
The problem I have is that we also have some evidence that the human lineage has more fixed genes than the chimp lineage:
quote:The team, which also included Rosaleen Gibbons, Lars J. Dugaiczyk, Thomas Girke, Brian Duistermars and Rita Zielinski, identified over 2,200 new human specific Alu DNA repeats that are absent from the chimpanzee and most likely other primates.
" The explosive expansion of the DNA repeats and the resulting restructuring of our genetic code may be the clue to what makes us human," Dugaiczyk said. “During the same amount of time, humans accumulated more genetic novelties than chimpanzees, making the human/chimpanzee genetic distance larger than that between the chimpanzee and gorilla.”
Metaphorically speaking, Dugaiczyk said, “Humans and other primates march to the rhythm of a drum that looks identical; the same size, shape and sound. But, the human drum beats faster.”
And having a different number of fixed genes also means a different rate of fixing genes - if we assume mutations average out to a relatively constant rate.
A different rate of fixing genes makes sense because there are several different selection processes going on, processes that necessarily run at different rates: genetic drift, survival selection and sexual selection. The relative importance of each process can shift depending on circumstances and behavior patterns.
(Note - Personally I think the reason for the higher human rate is sexual selection - if not runaway sexual selection - with the evidence being the apparent skin bareness, extremely long head hair, and a creative brain that increased in size until it endangers the life of the mother and child at birth - it's maxed out.)
So if we know that two branches have evolved at a different rate of fixing genes how can we assume a same or average rate anywhere else without it being suspect?
It seems to me that these genetic clock studies are looking at the data from the wrong viewpoint.
Rather than looking at the data and trying to develop an age from common ancestor based on assumed rates of mutation they should be looking at the data with all the current best fossil dating evidence for age from each common ancestor and be looking at what that means for the rate of fixing mutations in those populations.
Hi, I am someone who is both inquisitive and skeptical of Darwinian descent with modification.
This topic is specifically about the genetic information about a common ancestor to both humans and chimpanzees. To discuss this topic you need to read the referenced article and comment on what it says, not bring in other topics.
Your whole post is a much more general question that is beyond the scope of this thread - you should start a new topic for it or find an existing one that discusses general evolution questions.
I'll look forward to discussing your issues when you do that.
Replying to the part that is at least vaguely on topic:
quote:But the evidence suggests very strongly that humans did, in fact, evolve from a common ancestor
I make bold the word suggests which is used to suggests but still not a fact.
The genetic information is discussed in the article linked and referenced on Message 1. If you care to discuss that then point out the problems with the article.
Did you know that posting the same erroneous message you started with shows you haven't learned a thing? That is troll type behavior.
See responses to Message 68 for some comments relating to your claim here.
Please note that you need to substantiate your claim with the evidence -- something you have not done -- and that without substantiation all you have are words blowing in the wind.
Cite your sources.
...animals and humans have to share these things: 1)A heart 2)A brain 3)A digestive system 4)A stomach 5)Arms and legs 6)A circulatory system 7)A nervous system 8)A reproductive system 9) 2 eyes, 2 ears, a nose and a mouth 10)An endocrine system
quote:The sponges or poriferans (from Latin porus "pore" and ferre "to bear") are animals of the phylum Porifera. They are primitive, sessile, mostly marine, water dwelling, filter feeders that pump water through their bodies to filter out particles of food matter. Sponges also excrete sperm cells through these holes. Sponges represent the simplest of animals. With no true tissues (parazoa), they lack muscles, nerves, and internal organs.
You are so easily proven wrong about such a simple claim, could it be that your whole post is pure fabrication?
This specifically was pointed out on the previous thread linked above, and your failure to learn from it is noted as troll behavior.
Sorry, but humans are animals. Denial of this basic fact of biology does not change the fact that humans are animals. We are also mammals and primates and apes.
quote:Animals are a major group of organisms, classified as the kingdom Animalia or Metazoa. In general they are multicellular, responsive to their environment, and feed by consuming other organisms or parts of them. Their body plan becomes fixed as they develop, usually early on in their development as embryos, although some undergo a process of metamorphosis later on.
The word "animal" comes from the Latin word animal, of which animalia is the plural, and is derived from anima, meaning vital breath or soul. In everyday colloquial usage, the word usually refers to non-human animals. The biological definition of the word refers to all members of the Kingdom Animalia. Therefore, when the word "animal" is used in a biological context, humans are included.
Note the last line in particular. We are discussing the biology of humans and chimps on this thread, this is a science thread, and we use the scientific meanings of words to discuss science.
quote:Humans, or human beings, are bipedal primates belonging to the mammalian species Homo sapiens (Latin: "wise man" or "knowing man") in the family Hominidae (the great apes).[1][2]
(sidebar) Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Primates Family: Hominidae Genus: Homo Species: H. sapiens Subspecies: H. s. sapiens
And evolutionists are humbled indeed by making up impossible and ludicrous scenarios that even children can see are false until they ar brainwashed by those less intelligent as they are, simply because adults are stronger and more powerful than they are.
Ah yes the world wide disinformation conspiracy concept again. Please respond to How can Biologists believe in the ToE?, where your presence is requested to deal specifically with the ramifications of this claim. Be prepared to submit facts to substantiate your claims (something you seem particularly unable to do).
... since even CHILDREN know that animals don't turn into humans, then evolutionists don't even know as much as children know!!
Since evolution does not claim that animals "turn into" other animals, to say nothing of turning into humans, this is a straw-man argument, a falsehood, that even a child can comprehend leads to false conclusions. This too has been pointed out to you before.
There are four basic reasons for posting false information:
stupidity - you just don't comprehend that it is false,
ignorance - you don't know that it is false,
insanity - you believe it is true, and
maliciousness - lying, you know it is false but post it anyway.
We can also include delusional as a being between ignorance and insanity - in the context of having been mislead by others using false information that you then believe to be true because you trust those sources.
The test to distinguish ignorance (being deluded, a false belief, the state of being deluded) and insanity (fixed false belief resistant to reason or confrontation with fact) is the response to evidence that contradicts the belief in question.
We can eliminate ignorance by the presentation of information, as has been done. That leaves stupidity, insanity and lying (malicious) as possible alternatives.
So as jesus says; "HE who exalts himself will be humbled."
This thread is about the genetic difference between humans and chimps. Your original post was relevant to that topic, but this is not.
You were asked to substantiate your claim (Message 18) "that the DNA of mice and chickens is actually closer to the human DNA than apes and chimps" and you have not done so. This is a violation of forum guidelines.
Please cite your sources for the DNA information. Failure to do so will be construed as inability to do so, with the implication that your claim is false and you know it.
Please limit your posting to chimp and human DNA comparisons. That is the topic of this thread.
Anything else will be construed as disruptive troll behavior.
And these two statements: For years, the genetic similarity between humans and chimpanzees was put at 98.5%. The figure was then revised down to less than 95%.
And: "The similarities between mice and human DNA is 97.5 compared to 95 % between apes and humans."
I repeat: what is your source?
Either link a webpage or cite the relevant scientific journal article. Until you do so all you are doing is repeating an assertion that is unsubstantiated, and this is a violation of forum guidelines.
This is the third time I have asked for this information, and the conclusion I have to reach is that you do not have substantiation and are intentionally posting false information (whether you know it to be false or not is another question).
Failure to do so is a continued violation of forum guidelines.
Sorry but calling a human an animal because it's popular to do so no more makes a human an animal than calling a human a tree makes him a tree.
Popularity has nothing to do with it. A human is a animal because it has the characteristics of an animal. I'll put it a different way: there is no characteristic of "animal" that doesn't fit humans.
But it's too bad that scientists have to go into labs to try to define humans and animals, nor can they unbderstand why mice can't breed or change into humans. They therefore jump to impossible conclustions that can't happen in reality all because they don't know why humans and animals have similar genes. The theory of evolution is thus, much more bizarre and impossible than any other theory in the 19th century.
But I notice that the variations in DNA differs all over the web depending on who you talk to. So since scientists don't know, then obviously, no one can know.
That would by why you should refer to scientific journal articles rather than websites, and also why you should pay attention to what specifically is being compared. When you look at structural DNA elements the human and chimp DNA are 99% similar, but when you look at regulatory DNA elements the human and chimp DNA are 95% similar.
Your source is probably comparing structural DNA between mice\chicken and human versus regulatory (or overall) DNA between chimp and human: this is apples and oranges.
So pony up your source and lets see where the problem lies eh?
I would expect a high degree of similarity between species for genes that code for building blocks such as -keratins protein that are used to make hair, horns, nails, claws and hooves of mammals, because any change to the gene that affects how the protein is formed would change the protein.
This is simple back-thinking the issue: if the same protein is being used by two different organisms, then each has a gene to code for making it that results in the same protein. Such genes could be copied and mutated, but to achieve the same end result there has to be preserved the section that codes for the construction of the protein.
We also know that all life is based on a limited number of basic proteins, thus the genes that produce those proteins will need to be highly similar. Hair proteins are similar, bone proteins are similar, skin proteins are similar, etc etc.
In addition the basic "body plan" is also similar with number and placement of bones, organs and the like.
You could make an (probably bad) analogy to building a house and a five story apartment building using brick, wood, glass, metals and such. The instructions needed to make bricks, make mortar, make 2x4's, make nails, make glass, make pipes and ducts, etc. etc. would be the same for both building. Likewise the basic construction process used to build walls and windows and doors and floors would be the same, the only difference would be the repetitions, sizes and placement of each element -- the architectural plans. Summing up all the instructions necessary to build all the elements from scratch would mean that the regulatory (architectural) proportion would be fairly small compared to the structural proportion.
Thus I would expect parts of genomes that code for building proteins to be highly similar across species, but I would expect increasing differences in parts of the genomes that code for how to assemble those proteins for increasingly different organisms.
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