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Creationism/Evolution Title: Chimp puberty helps recalculate when chimps and humans split Recalibrated genetic evidence better matches the fossil record. A chimp in Leipzig Zoo contemplates its mutation rate. Genetic evidence is an incredibly useful tool for understanding evolutionary history. It has helped us build up our current picture of how humans migrated out of Africa and also estimate when chimps and humans parted ways from our last common ancestor. Estimates that used different methods have placed the chimp-human split anywhere from three million to 10 million years ago (mya), sometimes falling far from the estimated 6 to 7 mya suggested by the fossil record—an indication that something is wrong in the calculations. But as researchers improve their techniques, the estimates are revised over and over again, each time hopefully getting closer to the real picture. Having the dates provided by the fossil record match the genetic evidence would help us to be more sure of our understanding, so it’s important to try to work out where the mismatch is and why it’s happening. Two researchers at Columbia University, Guy Amster and Guy Sella, have suggested an important factor that has been missing: the timing of life events like puberty and reproduction and their effects on genetics. By building these factors into their calculations, they’ve come up with an estimate for the split that more closely matches the fossil records—around 6 mya. Slow or speedy mutation The genetic evidence that researchers used to estimate species splits like this comes from what's called a “molecular clock.” The principle is pretty simple: over time, DNA sees small mutations. Some of these changes make an important difference, but others are neutral—everything carries on the same before and after the mutation. These mutations happen at a certain rate. If we know that rate, we can see how many neutral mutations have accumulated in closely related species and use that to estimate when they started evolving separately. There are a couple of ways that the molecular clock can be calibrated: we can estimate it based on species that we’ve dated by other means (for instance, by the age of the rock layer they were found in) or by measuring the rates in species that are alive today. What Amster and Sella point out is that estimates of the chimp-human split haven’t taken into account some important complications in mutation rates, which means that the molecular clock isn’t properly calibrated. Most important, there are sex differences in mutation rates. One of these differences is in the creation of sperm cells and egg cells. The more often the germ cells that make them divide, the greater the chance of additional mutations. In female chimps and humans, as well as many other species, female sex cells do all their dividing before birth. This means that whether a female animal is twelve or twenty-four when it reproduces, it's using sex cell that has undergone the same number of divisions (with any ensuing mutations). As a result, the age of a female when it reproduces shouldn’t change the number of mutations passed onto its offspring. Males, on the other hand, see their sex cells undergoing divisions from puberty onwards. This means that a male reproducing later in life is likely to have a higher mutation rate in his sperm than if he reproduced earlier. This difference causes males to contribute more mutations than females, meaning that maternal and paternal lineages have differently calibrated clocks. There are also differences in mutation rates brought about by generation time. Because mutations accumulate from generation to generation, longer generation times mean fewer chances for mutations to build up. This means that the life cycles of different species will have different impacts on the mutation rates. So, when we estimate the human-chimp split based on the molecular clock, we need to take into account all this information, knowing when male chimps hit puberty (around 7.5 years, compared to humans’ 13 years), and what their generation times are like compared to humans. A recent division The authors found that when they included these factors in estimates of the mutation rates in humans and chimpanzees, the two lineages ended up with quite different rates, with humans experiencing a slower rate of mutation than our cousins. That in turn allows us to calculate a new estimate for when the human and chimpanzee lineages split. Far from the previous consensus date of 10 mya, the authors write, these techniques lead us to an estimate as early as 6.6 mya. It's exciting work, says Melissa Wilson Sayres, a computational biologist who wasn’t involved in the research. “This is a really brilliant paper,” she says, praising the authors for their “thoughtful and very clever approach.” It’s a problem she’s been thinking about for many years, she says, and this research is likely to be well-received by others in the field. Kevin Langergraber, who studies the behavioral and molecular ecology of chimpanzees and also wasn’t involved in the research, argues that it was premature to say that there was a consensus that the chimp-human split took place 10 million years ago. Wilson Sayres agrees, saying that rather than a consensus estimate, there’s been ongoing debate about the question. “The estimates have ranged from 5 million years to more than 10 million years ago,” she says. Nonetheless, says Langergraber, “this is a very interesting paper which will add to a growing body of literature,” exploring “more sophisticated estimates of split times.” Amster and Sella themselves point out that these estimates are still up for revision based on future work. For instance, there are certain kinds of mutations that could affect maternal sex cells, which would change the mutation rate for females. We also need to understand more about how sperm cells are generated in order to get an accurate estimate of timing there, too. (1 image) Post Comment Private Reply Ignore Thread Top • Page Up • Full Thread • Page Down • Bottom/Latest Still doesn't account for how we lost the opposable thumb on the foot another piece of crape trying to prove that humans aren't unique
#2. To: cranky (#0) The only love If you ... don't use exclamation points --- you should't be typeing ! Commas - semicolons - question marks are for girlie boys ! #3. To: paraclete (#1) (Edited) 'The find may be our first glimpse of a separate, extinct, branch of the human family, collectively called hominins. It also hints that there may have been several evolutionary paths leading to feet adapted for walking upright...." I personally don't find that threatening to the relationship between myself and my Creator. YMMV.
#4. To: VxH (#3) 'The find may be our first glimpse of a separate, extinct, branch of the human family, The real question is how we got here and where we came from. Explanations linking us to apes do have some gaps. We have abilities not shared with the apes. I don't believe the possibility that pond scum could become a human being, mutation are usually degenerate and we are only talking about the time since the last ELE and we seem to be in one right now. Consider the article released today which suggested that we hadn't made contact with any alien life form because life is easily extinguished, therefore we would appear to be the exception
#5. To: VxH (#3)
https://www.youtube.com/watch?v=UFc3DDTPXXo For when we were still without strength, in due time Christ died for the ungodly. For scarcely for a righteous man will one die; yet perhaps for a good man someone would even dare to die. But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us. (Romans 5:6-8) #6. To: cranky (#0) Estimates that used different methods have placed the chimp-human split anywhere from three million to 10 million years ago Is that a ballpark figure? For when we were still without strength, in due time Christ died for the ungodly. For scarcely for a righteous man will one die; yet perhaps for a good man someone would even dare to die. But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us. (Romans 5:6-8) #7. To: redleghunter (#6) Is that a ballpark figure? I think the 6-7 mya is a ballpark figure. The 3-10 mya sounds more like a wag. There are three kinds of people in the world: those that can add and those that can't #8. To: cranky (#7) I think the 6-7 mya is a ballpark figure. Good. What's one or two millions years with regards to scientific theory. For when we were still without strength, in due time Christ died for the ungodly. For scarcely for a righteous man will one die; yet perhaps for a good man someone would even dare to die. But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us. (Romans 5:6-8) #9. To: redleghunter (#8) What's one or two millions years with regards to scientific theory. Seems to depends on how much the grant was worth. For a couple more bucks, what number would you like? There are three kinds of people in the world: those that can add and those that can't #10. To: redleghunter (#5)
http://www.goodreads.com/book/show/816603.Sex_Evolution_and_Behavior
#11. To: VxH (#10) Meh...I think Pickett had it about right. For when we were still without strength, in due time Christ died for the ungodly. For scarcely for a righteous man will one die; yet perhaps for a good man someone would even dare to die. But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us. (Romans 5:6-8) #12. To: redleghunter (#11) Ordered 'im did he? Sounds like a Fallible and Uninspired assumption of dominion to me. Fortunately his state establishments lost the war.
#13. To: VxH (#12)
John 20: NKJV 24 Now Thomas, called the Twin, one of the twelve, was not with them when Jesus came. 25 The other disciples therefore said to him, “We have seen the Lord.” So he said to them, “Unless I see in His hands the print of the nails, and put my finger into the print of the nails, and put my hand into His side, I will not believe.” 26 And after eight days His disciples were again inside, and Thomas with them. Jesus came, the doors being shut, and stood in the midst, and said, “Peace to you!” 27 Then He said to Thomas, “Reach your finger here, and look at My hands; and reach your hand here, and put it into My side. Do not be unbelieving, but believing.” 28 And Thomas answered and said to Him, “My Lord and my God!” 29 Jesus said to him, “Thomas, because you have seen Me, you have believed. Blessed are those who have not seen and yet have believed.” For when we were still without strength, in due time Christ died for the ungodly. For scarcely for a righteous man will one die; yet perhaps for a good man someone would even dare to die. But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us. (Romans 5:6-8) #14. To: redleghunter (#13) (Edited) I think Jesus would've been perfectly comfortable with folks observing how natural selection was used to create the sexual exchange of genetic material - thus increasing the fitness of species for whom the Creator selected. The eunuchs and their Cesarean money changers, busily worshiping their created things... again -- probably not so much.
#15. To: cranky (#0)
For when we were still without strength, in due time Christ died for the ungodly. For scarcely for a righteous man will one die; yet perhaps for a good man someone would even dare to die. But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us. (Romans 5:6-8) #16. To: redleghunter (#15) Must be hot in those monkey suits, as a fashion statement it won't catch on
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