The jaw of Teinolophos trusleri catches the ear bones in the act of separating from the jaw.
Posted on 02/11/2005 6:49:09 AM PST by PatrickHenry
Triple bone structure arose independently in platypus and humans.
Listen up: mammals seem to have evolved the delicate bone structure of the middle ear at least twice. The surprising discovery comes from a fossil, found off the southern coast of Australia, that belongs to an ancestor of the platypus.
Modern mammals are unique among vertebrates for possessing three tiny bones in the middle ear. The malleus, incus and stapes (commonly known as the hammer, anvil and stirrup) work as part of a chain that transmits sound towards the skull. Birds and reptiles have only one bone to perform this function.
Because the mammalian arrangement is so complex, scientists believed that the set-up had evolved on just a single occasion, in an ancestor that gave rise to placental animals (including humans), marsupials and monotremes (such as the duck-billed platypus).
All this changed when James Hopson, a vertebrate palaeontologist at University of Chicago, Illinois, took a trip to Australia. There he met a team of researchers including Thomas Rich of Museum Victoria in Melbourne.
The jaw of Teinolophos trusleri catches the ear bones in the act of separating from the jaw.
Rich and his colleagues had recently unearthed a fossil of Teinolophos trusleri, an ancestor of modern monotremes that lived 115 million years ago. "He said he had some new Teinolophos specimens and when he showed them to me I almost fell off my chair," says Hopson, an author of the study, published this week inScience [Rich T. H., et al. Science 307, 910 - 914 (2005)].
Hammer time
Palaeontologists believe that the middle-ear bones of modern mammals once belonged to the jawbone and later separated to adopt their present location. This is supported by the fact that the middle ear's bones associate with the jaw in the early development of modern mammalian embryos.
What makes theTeinolophos specimen surprising is a large groove in its adult jawbone, which indicates that the smaller bones had not yet detached.
Teinolophos lived after monotremes split from the placental and marsupial mammalian groups. Its jawbone structure, along with its place in the evolutionary tree, hints that a common ancestor to all these mammals lacked the special three-bone ear structure.
This means that natural selection must have driven the same rearrangement in independent groups, after the monotreme split. "Some embryologists had the idea that it might be convergent but nobody really believed this," says palaeontologist Thomas Martin of the Senckenberg Research Institute in Frankfurt, Germany. "I was quite shocked when I heard that such a complex morphological transformation happened twice."
The discovery will compel many experts to rethink their appreciation of mammals' common evolutionary heritage. "Until now it was considered to be one of the most important shared derived characteristics of modern mammals," says Martin.
The trouble with the standard you propose is how will you know when a mutation has occurred, even if you are watching for it? Why must the first person who exhibits a new trait be the same person as the first person who inherits a mutation? Many mutated genes are recessive, and their effects may not show up for hundreds or thousands of years after the mutation occurs. The only way that a mutation which is recessive would show up would be after there has been sufficient inbreeding in the population to make a heterozygous recessive individual a reasonable possibility. In other organisms, this is much less problematic than in humans, since humans have laws that prevent inbreeding, at least for several generations.
That's like saying being born without eyes is an advantage because it prevents myopia.
No, if malaria is the primary cause of premature death in a human population in a given environment (premature death = death occurring before reproduction), then a mutation that causes premature death in homozygous individuals, but prevents premature death iin heterozygous individuals would be beneficial if the mutated allele were present in the proper frequency. Ie. common enough to make it likely that an individual would have one copy of the allele, but not so common that the individual would be likely to have two copies. Again, what is beneficial depends on environmental factors. A beneficial trait in one environment might be neutral or harmful in a different one.
I'm not really proposing a standard. I'm just wondering if we've ever actually caught evolution in the act in humans. If we haven't, that doesn't mean it's wrong. You know, the old "lack of evidence" vs. "evidence of lack" thing.
All of which begs the question, for what possible purpose would a designer give a human population a gene which is lethal in homozygous individuals? Why would there be any lethal genes at all if humans were designed? I have read that all humans have several hundred genes that are potentially lethal in homozygous individuals. (sorry I can't remember where I saw this so I can't provide a source) Why would a designer put them there?
Whether we've seen evolution in humans is a different matter from detecting a new mutation. Evolution is the variation over time of allele frequencies in a population of organisms. I don't know whether any real studies of allele frequencies in humans have ever been done or not, but now that we can sequence genomes, it should be easier to detect a shift in allele frequencies. Previous to the ability to do genetic sequencing, only phenotypes, not genotypes would have been determinable, so I'm not sure if it would be possible to conclusively observe evolution in a human population, although I would guess that a study of the relative frequency of certain phenotypes would enable scientist to say something about genotype frequencies.
"I want to know why homo sapiens was SO much better at survival no Neanderthal are still around..."
Cro-Magnon ate him. :}
"I would think Victoria was a bit young to be responsible for the hemophilia in the Romanovs...but of course I could be wrong.
More to the point, hemophilia isn't a useful adaptation. It doesn't contribute to survival. (I know that you weren't claiming it was; you were making another, quite valid point.) All of the mutations I've ever heard of in humans are actually detriments to survival, causing conditions like cystic fibrosis, hemophilia, beta thalassemia, or Down syndrome. When was the last positive, advantageous mutation in humans? Shouldn't there have been one in recorded history?"
The case against Victoria is well established - she was queen for something like 70 years and had a large family. One of her daughters is responsible for passing that gene around, including to the Romanov's.
Those genetic diseases you mention are, yes, not good. BTW because we keep these people alive longer that they would have survived 1000 years ago, we not only keep those genes in our pool, but actually increase their frequencies.
Would you actually see an advantageous gene if it was in front of you? But look at some simpler things. Why are most native peoples of the tropics dark skinned? The only native blond haired, blue eyed populations are northern latitude. Is that a coincidence? Black people from Africa that are heterozygous sickle cell have increased malaria resistance. Is this going somewhere? It is well known, but not hyped, that people with higher IQ's tend to have children with higher IQ's. I think that is as good an example as one can find.
If we allowed eugenics, we might pull some of these "advantageous" genes out so they would be more visible (please do not accuse me of advocating eugenics).
What I am saying is that these "advantageous" genes are there, but not obvious. Since we so readily mix worldwide and we interfere with the natural course in our own evolution by keeping people alive that in a wild state would be quickly weeded out, it seems to me that we are doomed to be a dead end species.
Romans 5:12-21
12. Therefore, just as sin entered the world through one man, and death through sin, and in this way death came to all men, because all sinned--
13. for before the law was given, sin was in the world. But sin is not taken into account when there is no law.
14. Nevertheless, death reigned from the time of Adam to the time of Moses, even over those who did not sin by breaking a command, as did Adam, who was a pattern of the one to come.
15. But the gift is not like the trespass. For if the many died by the trespass of the one man, how much more did God's grace and the gift that came by the grace of the one man, Jesus Christ, overflow to the many!
16. Again, the gift of God is not like the result of the one man's sin: The judgment followed one sin and brought condemnation, but the gift followed many trespasses and brought justification.
17. For if, by the trespass of the one man, death reigned through that one man, how much more will those who receive God's abundant provision of grace and of the gift of righteousness reign in life through the one man, Jesus Christ.
18. Consequently, just as the result of one trespass was condemnation for all men, so also the result of one act of righteousness was justification that brings life for all men.
19. For just as through the disobedience of the one man, the many were made sinners, so also through the obedience of the one man the many will be made righteous.
20. The law was added so that the trespass might increase. But where sin increased, grace increased all the more,
21. so that, just as sin reigned in death, so also grace might reign through righteousness to bring eternal life through Jesus Christ our Lord.
and now we have NAMBLA........
A lot of our problems are due to aging. Most quadrapeds don't live very long. How much this impacts what you guys are saying, I'm not sure.
I'm sorry, Elsie, NAMBLA ain't in my lexicon.
Here's one discovered in the last few years: Gene mutation makes baby super strong
Cheers!
Hard to guess if that's really an advantageous mutation or not.
I've heard rumors that some of our blood types are turning out to be rather recent, and are speculated to have evolved to enable us to deal with differing dietary regimes that have emerged with the advent of husbandry and farming.
Alexandra Feodorovna was a granddaughter of Queen Victoria.
And why would Adam being symbolic render Jesus symbolic too? Is the message of the Bible, for you, a house of cards that will collapse if the creation story is an allegory like all the other creation stories across the world? Most Christians seem to be doing just fine reconciling the Bible and reality of God with an ancient earth and universe.
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