Australopithecus Sibeda
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http://news.yahoo.com/closest-human-ancestor-may-rewrite-steps-evolution-141606435.html
Our Evolution
LiveScience.comBy lt | LiveScience.com – 4 hrs ago
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* This image released by the journal Science shows the right hand skeleton of the adult female Australopithecus sediba against a modern human hand. A detailed analysis of 2 million-year-old bones found in South Africa offers the most powerful case so far in identifying the transitional figure that came before modern humans, findings some are calling a potential game-changer in understanding evolution. The hand, seen in a palmar view, lacks three wrist bones and four terminal phalanges, but is otherwise complete. (AP Photo/Peter Schmid, courtesy of Lee Berger and the University of Witwatersrand)View Gallery
This image released by the journal Science shows the right hand skeleton of the adult …
A startling mix of human and primitive traits found in the brains, hips, feet and hands of an extinct species identified last year make a strong case for it being the immediate ancestor to the human lineage, scientists have announced.
These new findings could rewrite long-standing theories about the precise steps human evolution took, they added, including the notion that early human female hips changed shape to accommodate larger-brained offspring. There is also new evidence suggesting that this species had the hands of a toolmaker.
Fossils of the extinct hominid known as Australopithecus sediba were accidentally discovered by the 9-year-old son of a scientist in the remains of a cave in South Africa in 2008, findings detailed by researchers last year. Australopithecus means "southern ape," and is a group that includes the iconic fossil Lucy, while sediba means "wellspring" in the South African language Sotho.[See images of human ancestor]
Two key specimens were discovered — a juvenile male as developed as a 10- to 13-year-old human and an adult female maybe in her late 20s or early 30s. The species is both a hominid and a hominin — hominids include humans, chimpanzees, gorillas and their extinct ancestors, while hominins include those species after Homo, the human lineage, split from that of chimpanzees.
To begin to see where Au. sediba might fit on the family tree, researchers pinned down the age of the fossils by dating the calcified sediments surrounding them with advanced uranium-lead dating techniques and a method called paleomagnetic dating, which measures how many times the Earth's magnetic field has reversed. They discovered the fossils were approximately 1.977 million years old, which predates the earliest appearances of traits specific to the human lineage Homo in the fossil record. This places Au. sediba in roughly the same age category as hominids such as Homo habilis and Homo rudolfensis, which were thought to be potential ancestors to Homo erectus, the earliest undisputed predecessor of modern humans. [10 Things That Make Humans Special]
"As the fossil record for early human ancestors increases, the need for more accurate dates is becoming paramount," said researcher Robyn Pickering at the University of Melbourne in Australia.
Small but humanlike brain
Most aspects of Au. sediba display an intriguing mix of both human and more primitive features that hint it might be an intermediary form between Australopithecus and Homo.
"The fossils demonstrate a surprisingly advanced but small brain, a very evolved hand with a long thumb like a human's, a very modern pelvis, but a foot and ankle shape never seen in any hominin species that combines features of both apes and humans in one anatomical package," said researcher Lee Berger, a paleoanthropologist at the University of Witwatersrand in Johannesburg, South Africa. "The many very advanced features found in the brain and body and the earlier date make it possibly the best candidate ancestor for our genus, the genus Homo, more so than previous discoveries such as Homo habilis."
The brain is often thought of as what distinguishes humanity from the rest of the animal kingdom, and the juvenile specimen of Au. sediba had an exceptionally well-preserved skull that could shed light on the pace of brain evolution in early hominins. To find out more, the researchers scanned the space in the skull where its brain would have been using the European Synchrotron Radiation Facility in Grenoble, France; the result is the most accurate scan ever produced for an early human ancestor, with a level of detail of up to 90 microns, or just below the size of a human hair.
The scan revealed Au. sediba had a much smaller brain than seen in human species, with an adult version maybe only as large as a medium-size grapefruit. However, it was humanlike in several ways — for instance, its orbitofrontal region directly behind the eyes apparently expanded in ways that make it more like a human's frontal lobe in shape. This area is linked in humans with higher mental functions such as multitasking, an ability that may contribute to human capacities for long-term planning and innovative behavior.
"We could be seeing the beginnings of those capabilities," researcher Kristian Carlson at the University of Witwatersrand told LiveScience.
These new findings cast doubt on the long-standing theory that brains gradually increased in size and complexity from Australopithecus to Homo. Instead, their findings corroborate an alternative idea — that Australopithecus brains did increase in complexity gradually, becoming more like Homo, and later increased in size relatively quickly.
Modern hips
This mosaic of modern and primitive traits held true with its hips as well. An analysis of the partial pelvis of the female Au. sediba revealed that it had modern, humanlike features.
"It is surprising to discover such an advanced pelvis in such a small-brained creature," said researcher Job Kibii at the University of the Witwatersrand. "It is short and broad like a human pelvis ... parts of the pelvis are indistinguishable from that of humans."
Scientists had thought the human-like pelvis evolved to accommodate larger-brained offspring. The new findings of humanlike hips in Au. sediba despite small-brained offspring suggests these pelvises may have instead initially evolved to help this hominin better wander across the landscape, perhaps as grasslands began to expand across its habitat.
When it came to walking, investigating the feet and ankles of the fossils revealed surprises about how Au. sediba might have strode across the world. No hominin ankle has ever been described with so many primitive and advanced features.
"If the bones had not been found stuck together, the team may have described them as belonging to different species," said researcher Bernhard Zipfel at the University of the Witwatersrand.
The researchers discovered that its ankle joint is mostly like a human's, with some evidence for a humanlike arch and a well--efined Achilles tendon, but its heel and shin bones appear to be mostly ape-like. This suggested the hominid probably climbed trees yet also halkid in a unique way not exactly like that of humans.
Altogether, such anatomical traits would have allowed Au. sediba to walk in perhaps a more energy-efficient way, with tendons storing energy and returning that energy to the next step, said researcher Steve Churchill from Duke University in Durham, N.C. "These are the kinds of things that we see with the genus Homo," he explained.
What nice hands …
Finally, an analysis of Au. sediba's hands suggests it might have been a toolmaker. The fossils — including the most complete hand known in an early hominin, which is missing only a few bones and belonged to the mature female specimen — showed its hand was capable of the strong grasping needed for tree-climbing, but that it also had a long thumb and short fingers. These would have allowed it a precision grip useful for tools, one involving just the thumb and fingers, where the palm does not play an active part.
Altogether, the hand of Au. sediba has more features related to tool-making than that of the first human species thought of as a tool user, the "handy man" Homo habilis, said researcher Tracy Kivell at the Max Planck Institute for Evolutionary Anthropology in Germany. "This suggests to us that sediba may also have been a toolmaker."
Though the scientists haven't excavated the site in search of stone tools, "the hand and brain morphology suggest that Au. sediba may have had the capacity to manufacture and use complex tools," Kivell added.
The researchers do caution that although they suggest that Au. sediba was ancestral to the human lineage, all these apparent resemblances between it and us could just be coincidences, with this extinct species evolving similar traits to our lineages due, perhaps, to similar circumstances. [Top 10 Missing Links]
In fact, it might be just as interesting to imagine that Au. sediba was not directly ancestral to Homo, because it opens up the possibility "of independent evolution of the same sorts of features," Carlson said. "Whether or not it's on the same lineage as leading to Homo, I think there are interesting questions and implications."
The scientists detailed their findings in the Sept. 9 issue of the journal Science.
[edit: added photos from article -- natural]
-- I feel so much better since I stopped trying to believe.
"We are entitled to our own opinions. We're not entitled to our own facts"- Al Franken
"If death isn't sweet oblivion, I will be severely disappointed" - Ruth M.
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Most of it is vague/speculative, preliminary suggestions about how significant this find is, and some of it is self-contradictory. It belongs to the Australopithecus genus, yet is also a hominin, or a species derived from the genus Homo, yet it is also a potential "ancestor for our genus, the genus Homo". If nothing else, this article suffers from highly confusing and poorly done editing, and it may have even been dumbed down for the masses by the people publishing this article.
“A meritocratic society is one in which inequalities of wealth and social position solely reflect the unequal distribution of merit or skills amongst human beings, or are based upon factors beyond human control, for example luck or chance. Such a society is socially just because individuals are judged not by their gender, the colour of their skin or their religion, but according to their talents and willingness to work, or on what Martin Luther King called 'the content of their character'. By extension, social equality is unjust because it treats unequal individuals equally.” "Political Ideologies" by Andrew Heywood (2003)
I've been disappointed with a lot of science reporting these days, especially Science Daily (this article is not from them).
But anyway, the reporting might not be too great on this one, but the bones are still going to be there at the end of the day.
For a really good program on Human evolution, there was one on a local PBS station recently as a 3 part Nova miniseries: http://www.pbs.org/wgbh/nova/evolution/becoming-human-part-1.html
Even I learned quite a few interesting things from this program, and I considered myself pretty well-informed on the latest science. Highly recommended.
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What's wrong with this article?
Random misspellings and the contradictions that Kapkao observed suggest that it was not properly proof read before it was published.
And yes, I agree that science reporting is not what it used to be. For one example, years ago, Scientific American used to do fairly long articles on the main topics. Today, they have added like 50-60 pages of short works, many small enough to get two or three items on one page. To do that, they have sacrificed the main articles by cutting them down to 3 or 4 pages.
Currently, New Scientist is the place that I go for a great deal of reading. Most articles are linked to a relevant paper on arXiv.org.
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I don't know what Kapkao had in mind, but I disliked the hyperbole about 'overturning' how we think about human evolution. It will not overturn anything. It will just add more and more understanding, flesh out details and relationships, and give us insights into what other questions we can explore. I don't like that kind of hyperbole because it gives the general audience a false idea of how science works.
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Agreed. It just fuels the theist assertion that science keeps changing its mind. As if science was a thing which could have a mind to change.
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http://m.yahoo.com/w/news_america/closest-human-ancestor-may-rewrite-steps-evolution-141606435.html?orig_host_hdr=news.yahoo.com&....
Heathensrule!
I deny the existence of the Holy Spirit!
Contradictions may not actually be contradictions. We already know human ancestors mated with neanderthals. Who's to say there wasn't a few different prehumans who got it on? It could explain a few things about our origins, and what happened to our distant cousins.
Enlightened Atheist, Gaming God.
There's hummins mating with ape-man 1.97 million years ago? Maybe Homo Habilis, instead? Even then, you have to figure out what species the half-breed belongs to, and perhaps taxonomy has already devised a means to do this, but I'm not aware of it. Remember that whatever species this supposed half-breed is, ultimately, it's also supposed to be the direct ancestor of the human race. So either it's a 'mule' and can't produce healthy offspring nor can it belong to it's own species, it is a fully functional hybrid creature and does qualify as a separate species, or it isn't a hybrid at all. Did Neanderthals and humans produce fertile offspring? Could creatures of differing genii do so?
It's a stretch, to be sure.
“A meritocratic society is one in which inequalities of wealth and social position solely reflect the unequal distribution of merit or skills amongst human beings, or are based upon factors beyond human control, for example luck or chance. Such a society is socially just because individuals are judged not by their gender, the colour of their skin or their religion, but according to their talents and willingness to work, or on what Martin Luther King called 'the content of their character'. By extension, social equality is unjust because it treats unequal individuals equally.” "Political Ideologies" by Andrew Heywood (2003)
According to the latest research, if you have a significant amount of European ancestry, you are very likely to have between 1% and 4% of Neanderthal DNA in you.
Interbreedings do not have to be impossible for two species to really be two species. They just have to be sufficiently uncommon in practice that gene flow between the species is so low as to keep the species distinct over geological time. Many drastically different species of plant readily hybridize under artificial breeding. Many species of large cats are capable of fertile offspring, if artificially mated. It's just that these matings don't occur hardly at all in natural settings.
Homo sapiens and Homo neanderthal definitely produced fully functional hybrids, and these became the ancestors of modern European lineages. Fact.
They are still two separate species, with very different physiology, diet, and metabolism. Neanderthals were almost exclusively meat eaters, with very little evidence of eating fruits, such as wild berries, even though such things were widely available in their habitats. They were predators of large game, such as mammoths. Their daily energy intake is estimated at around 5000 calories, about as much as someone competing in the Tour de France. Average human (sapiens) energy requirements are more in the neighbourhood of 2000 calories or less.
Even with this consideration, you are probably close to the mark when you say that such hybrids make the idea of being separate species less clear. It is possible that one of the reasons neanderthals went extinct is through interbreeding and 'absorption' into a much larger sapiens population. The neanderthal populations were quite sparse due to their predatorial lifestyle. Sapiens, with its much lower energy requirements, ability to utilize vegetation in its diet, more advanced tools and culture, and larger population density, probably overwhelmed the European neanderthal population. Interbreeding or no, the competition would have been intense, and the neanderthals (obviously) didn't stand a chance.
Perhaps neanderthals and humans were still so closely related that interbreeding was easier and more frequent, making the line between their species more blurry. That's not an unrealistic idea.
Perhaps australopithicenes and other ape/homo transitional species were also so closely related that interbreeding and hybridization occurred more frequently than in typical species. That's not unreasonable either. Personally, I'm beginning to suspect that it is more likely the case than not!
I wouldn't be surprised--in fact I'm willing to make a strong prediction right now--that there is far more interbreeding between sister species in the lead-up to Homo sapiens than we currently suspect.
I'll make another prediction: I expect that in the next 20 years, we will discover several new, previously undiscovered, species in our extinct family tree (cousin species as well as direct ancestors), and that there will be growing evidence of interbreeding between several of those species.
The picture I'm forming in my mind was heavily influenced by that Nova series I linked to. It also had some ugly hyperbole in it, but overall it was a very informative program.
The picture is of an ancient African savannah newly colonized by strange, two-legged hominids who find themselves in a brand new, wide open country with all sorts of new ways to live and grow into. There is a rapid radiation of species from one or a few to many. Each expands to fill a particular niche. But the environment of this ancient savannah changes so rapidly that there is a lot of upheaval, dislocation, and ultimately inter-mixing of these different species, that they cannot really maintain geological-time separation from one another, and so there is above-normal interbreeding and gene-flow.
This leads to a much more tangled family tree than is typical, and so the genes that provide advantage for those who live a more generalized, adaptable lifestyle will come to be favoured over time. And so, you get several closely related species giving rise to successive species that are more adaptable, and generally more intelligent than their ancestors.
Until finally, today, we have a species that interbreeds freely, and is adaptable to nearly every environment on the planet--and even off-planet.
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Thanks, Natural -- I was just too lazy.
You guys do realize that it's a GOOD thing that science changes it's views on things right?
ditto...
Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality
"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris
The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me
From the sublime to the ridiculous: Science -> Philosophy -> Theology
Briefly - I thought it was fun and interesting they had identified a new species with such a mix of characteristics and the fossil was so complete.
Secondly - "species" is a fluid concept and biologists are still arguing over what it exactly is to be a species. I usually stick with "a reproductively isolated population" as a general concept - but it is very general and very fuzzy in the real world. For a very common and well known example - dogs, wolves, coyotes, African wild dogs, all canids, can interbreed and produce viable offspring. I don't know of any reason other species - including homo - may not have gone through a similar evolutionary stage. We can't test it out nowadays as we seem to have managed to out compete all other closely related species and the ones that are left to interbreed with are not biologically close enough to us.
It is not unusual for the real fossil record to be a tangled mess. It really is true we can not determine which ancestor fossil lead to which living species. I've seen where horses, for example, are also not straight forward. As we find more fossils, I would bet other lineages also are just as tangled. Evolution is never a tree, or even a bush. Instead, we have good evidence it is just the opposite - lots of related species gradually reduce to a few or even one living species.
When the environment changes enough to put evolutionary pressure on the species within that environment, it is very possible to get an "explosion" of new species. As various organisms vie for survival in the new ecological niches, rapid development of new forms may occur. You get parallel and convergent evolution. Until eventually, a few species get the hang of it and out compete all the others.
-- I feel so much better since I stopped trying to believe.
"We are entitled to our own opinions. We're not entitled to our own facts"- Al Franken
"If death isn't sweet oblivion, I will be severely disappointed" - Ruth M.
I think it is a wonderful thing. Why would anyone want knowledge to be static?
Never mind.....
-- I feel so much better since I stopped trying to believe.
"We are entitled to our own opinions. We're not entitled to our own facts"- Al Franken
"If death isn't sweet oblivion, I will be severely disappointed" - Ruth M.
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OK Natural, I agree but with modification.
The concept of a species predates Darwin by a few decades and thus is connected with the idea that there are different “kinds” of critters. The modern understanding is that different populations are related to some specific degree and the closeness of the relationship determines how they may interbreed.
Thus, pick an animal from Maine and it may not be capable of breeding with the very similar animal from Florida. Yet there may well be a chain of possible breeding of, say, the Maine population can breed with the Vermont population which can breed with the Massachusetts population which can breed with the Connecticut population and so on down the line.
You mentioned the order felidae specifically. With genome sequencing, it has now been determined that domestic cats are most closely related to north African wild cats. Hardly surprising when you consider that we all lived there when they started hanging out with us but today, we have actual evidence for the matter.
Even so, I spent 18 years with a Bengal. They are part Asian snow leopard. I got mine for free but if you go to a breeder, expect to pay north of $500 for a kitten. Situation will be changing though as it turns out that the wild genes render them immune to a bunch of things that turn up in intentionally bred domestic cats. FIV (kitty AIDS) being the big one for most people. There is a small but growing market for people getting Bengals for out breeding.
There are also Savannah cats which are part African Serval. We don't yet know about the disease resistance on that breed but it is at least probable. That breed is so new that you can plan on going north of $2,000 per kitten though. Still, I expect that they are likely going to end up in the general gene pool in a few years.
In a couple of decades, the concept of a house cat could well be very different from what we know today.
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Uh duh..... me no unner stan kwestchun. What sci-unnz iz?
Of course we do. You do realize that science doesn't typically progress by 'overthrowing' theory after theory at every fossil find the media bothers to report about, right?
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yus but i liek mudkips du u?
Of course reporters tend to want to sell the story, but if it sells science then I'm all for it as long as they don't simply make shit up.
It's a fact that saying "We found a fossil that could very well overturn some common conecptions on evolution!!" will sell more than "Fossil of primate 485672 tends to exhibit traits that were once thought to have not existed at that time."
On that note if they said "HOLY SHIT EVOLUTION WAS TURNED ON IT"S HEAD!!!!" then yeah, stuff like that would turn off most scientists and give the creationists a boner.
It's a science article, not a journal and should be made accessiable in a way to the public. They can't just go on about the complex theory of evolution, because some people with little science training should be able to read it and understand it. The complex in depth stuff is resereved for peer reviewed journals.
Not me. It's not selling science if it's just selling the findings of some scientists. Selling real science should be selling how science works, comparing evidence for different theories and showing why some new evidence provides more weight to one theory than the other. This article basically just declared that it was the case without spending much time making the actual case.
Selling science trivia is not the same as selling science.
You underestimate the capacity for people to learn and understand science and evolution, and overestimate the difficulty of communicating science and evolution.
Evolution is not actually that complex. It's actually a very simple idea at its basis. Five ideas: Generation, Variation, Communication, Selection, and Iteration. Or two if you want to super-simplify it: Sex and Death. You don't need a PhD to understand it. Anyone at a high-school level (and many even younger) can learn it if their head isn't pre-filled with anti-science dogma.
I'm not calling for abstract jargon and obfuscation.
I'm calling for clarity and accuracy instead of hype.
Neither of those require sacrificing readability by the public at large.
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something about edits not working...
le sigh
wtf? triple post?
Hold... one friggin moment. If you are responding to me, I did not say that and even were I appear to imply such, that is not my meaning. I can't take credit for this.
My response to Vastet is that, well... a fertile hybrid of different species is possible, but how often do they become fertile? What determines the occurrence of fertile offspring? A few extra chromosomes that lead to a failed zygote? And, lastly, that fertile offspring between two genii is a stretch. At least, it is based on my current knowledge. So, what is the likelihood that this creature contributed to our genome from... multiple species, and almost 2 million years ago.
Yes, yes... the much more specialized organism gives way to the more easily adapted generalist as soon as its niche disappears. Classic story happening all the time through natural history, and it happened yet again with cro-magnon man and neanderthals. As it happens, I already know much of what you say... save for the lower energy requirements of homo sapiens. It also just happens that all of your predictions are worded just generally enough to be fairly safe guesses. Biology is a fairly fluid and chaotic science. Add to that the reliability of the fossil record, and you are left with an entire field of study dedicated to learning things about extinct animals by looking at the structure of it's bones. Or a jaw fragment, sometimes. Maybe a few teeth still attached. A hand or paw with a few missing digits. You get the idea.
If it's possible with the confines of an animal species' psychology and its chemistry to act in a specific manner, it's a given that at least one member of such a species will indeed act in such a manner. Meaning, mating between similar species is almost a given.
I'm not here to dispute that. But I am both curious and dubious of what it has to do with the genome of the species I belong to. That science will eventually proclaim words to the effect off "Oh, this Sibeda species isn't as closely linked to modern man as we originally thought" is also a fairly safe guess.
Ok, AiGS apparently went ahead posted or related much of the remainder of what I was going to post. That'll teach me not to read the rest of the thread before typing.
“A meritocratic society is one in which inequalities of wealth and social position solely reflect the unequal distribution of merit or skills amongst human beings, or are based upon factors beyond human control, for example luck or chance. Such a society is socially just because individuals are judged not by their gender, the colour of their skin or their religion, but according to their talents and willingness to work, or on what Martin Luther King called 'the content of their character'. By extension, social equality is unjust because it treats unequal individuals equally.” "Political Ideologies" by Andrew Heywood (2003)
I agree. I think the science is amazing. I only had minor complaints about the reporting of it. Really, this is not that bad of an article. Most of my ire comes from other recent articles; the name Science Daily being a frequent source of it.
Just wanted to highlight this bit. This is a very good way of thinking about it and describing it. Your other points about the 'species' concept were excellent, too.
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I've got a new (sorta) word to promote.... Learning.
Science learns. Evolution learns. Brains learn. Atheists who give up theism do so by learning.
This is to counter the fundie idea that if science 'changes all the time', that it's a bad thing. Well, I change all the time, too. When I believe something wrong, and I encounter new information that exposes my error, I stop believing the wrong thing and eventually come to a better understanding. It's called 'learning'. It's a good thing, not a bad thing. Who would want to believe in a dogma that forbids learning?!
That's what religion/creationism does: New evidence?! Ignore it! Pretend it doesn't exist. God forbid we might learn something new!
It's also a good metaphor for how evolution works, by a kind of trial and error learning process. Ideas (species, organisms, genes) that work are kept around because they work, and ideas that don't work are forgotten because they don't work all that well. And sometimes, unfortunately, they are just forgotten for no good reason. But overall, barring major catastrophes (which certainly do occur), evolution continually learns new ways for life to eke out a living in a changing environment.
You can even connect the learning metaphor to artificial intelligence, specifically the branch known as machine learning. This is useful to explain the idea that evolution is a form of undirected, non-conscious learning, just like how Google or Facebook automatically learn what websites or friends you might like based on things you already searched for and whatnot. No actual person/mind is required for this to work, it just happens automatically because it is a learning system. Just like how evolution is a learning system, and doesn't require a person/mind for it to work.
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The concept of a species is a) a word of convenience, b) mostly arbitrary, c) tailored to fit our various sub-theories within evolution.
For example, the concept of a species does not really make much sense in the world of bacteria, which usually don't have 'sex' or 'interbreed', but on the other hand have multifarious ways of sharing genetic information between individual bacterial cells.
In fact, if you read Dawkins' The Selfish Gene--which I highly recommend to anyone (I read it again just recently after several years, and it still sparked a whole bunch of new insights this time around)--evolution doesn't work on species at all, or even individual organisms, but on genes themselves.
It just so happens that some genes are stuck to other genes on a single strand of DNA called a chromosome, that tends to get replicated all-at-once so these various genes, like team members in a rowing boat, either work like a team and win, or fail to work like a team and lose.
And these chromosomes happen to inhabit little cells, and so the genes in one cell either work together to operate the cell efficiently and win, or fail to do so and lose.
And some of these cells happen to live in little (or big) collectives, and they either work together as an organism and win, or fail to and lose.
Etc. Etc.
The idea of a species is like a Cartesian grid or a pixelized bitmap overlaid on top of a smooth, continuous curve. It works for the most part, but if your resolution scale is too low, you end up with a blurry picture and unexplained artifacts (e.g. aliasing on the bitmap side of the metaphor, weird hybrids on the evolution side of the metaphor).
But on the other hand, when dealing with phenomena at truly larger scales, if you try to use a species concept that is too high resolution, you end up with over-detailed models that are bulky and hard to use in practice.
It's always going to be a compromise. You basically have to pick the species concept that best suits the task you're trying to accomplish. Jerry Coyne has several good posts on his website about this (google: biological species concept).
All that being said, the widely known and generally used concept of 'does it successfully interbreed or not' is a pretty good compromise for most purposes that the general public is going to need to deal with on a daily basis.
And with that being said, I come to my final point: All that really matters is what genetic information gets transmitted from one generation to the next. It's that raw genetic variation in information that evolution works on. The species concept is just a particular lens you put on to focus on the patterns you're interested in looking at. Evolution's going to keep on going the way it goes regardless of which lens you use to look with.
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Sorry for not quoting the context previously. Here's what I was responding to:
There appeared to me to be a few things going on there, causing some confusion.
My response to you was meant to try to clarify these issues.
How often? We don't know, in this case. It depends on the different species. Some related species diverge very quickly. Some related species remain inter-fertile for very long periods, even though there may not have been any actual interbreeding for millions of years.
No one has ever tried this, and the ethics of it are unclear, but it has been suggested that humans and chimps, being so closely related, could possibly be artificially interbred to produce a living hybrid. We have only been separated for about 5 million years, give or take. Other inter-fertile species have been separated for longer than that.
Would such a chuman or himp or humanzee be fertile itself? We don't know. It's possible. It's not completely out of the question. It's not very probable, but it's also not so improbable as to be ruled out.
This latter--raising a hybrid to the point of testing its fertility--will probably not be tried, due to ethics. But imagine if some group tried to do an interbreeding, just to see, and then aborted the fetus before it got too far along. Would that actually be unethical? Hard to say. What if a human female volunteered to be the temporary mother, instead of forcing a chimp to do it? Hard to say.
Regarding extra chromosomes: Humans have 23 pairs. Chimps have 24. The difference is not large, and human chromosome 2 is made up of ancestral DNA from two chromosomes that remained separate chromosomes in chimps. It's basically all the same 'volumes' in the 'encyclopedia', but our B volume was made by gluing the ancestral K volume to the ancestral S volume (or whatever).
Also, most of our human ancestors probably had only 23 pairs, as well, because the merging of chromosome 2 occurred quite a long time ago.
So extra chromosomes probably wouldn't be a problem for pre-human interbreeding.
There are five major mechanisms by which inter-species breeding is typically prevented:
Again, like species, the genus concept is largely an arbitrary line drawn in the sand. In the case of humans (Homo vs. non-Homo) even more so, because we basically just conjure up whatever we can think of that makes us 'distinctly' human, and call that 'Homo'. There really is no such single thing. It's a continuum, a smooth curve, not a sharp cliff.
Humans are very very very closely related to chimps, whose genus is Pan. It's possible we might even be able to interbreed with them. Not probable, but possible.
Between Homo and Pan, there are at least 4, probably more, intermediary 'genii'. The chance that Homo could interbreed with an intermediate genus is at least as probable as interbreeding with Pan, with the probability increasing the closer the relationship. Let's just say that it wouldn't surprise me if two neighbouring genii in that transition (say, Ardipithecus and Australopithecus) could interbreed occasionally successfully--enough to influence our eventual makeup.
Sorry. Not meaning to lecture you. I also write with other forum readers in mind who may not know as much background info.
That's what makes science so fascinating, in my opinion. Nearly every scientific discovery is counter-intuitive, because if it had been intuitive in the first place, we would have already known it before-hand!
It's an endless source of surprise. Like a never-ending birthday present.
I agree with the last sentence; that's along the lines of what I was complaining about regarding over-hyping of new findings.
As for how our genome has been affected by inter-species gene flow? Well, neanderthal, for one. Apparently there is also evidence of crossover with Denisova hominin as well, though I'm much less familiar with that news. The rest of what I said was just my own speculations, not science per se.
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Are you going to pull your pants down and show us your rear end as well? I must warn you... AiGS might like that. I, on the other hand... have standards. TDS is the only woman for me.
“A meritocratic society is one in which inequalities of wealth and social position solely reflect the unequal distribution of merit or skills amongst human beings, or are based upon factors beyond human control, for example luck or chance. Such a society is socially just because individuals are judged not by their gender, the colour of their skin or their religion, but according to their talents and willingness to work, or on what Martin Luther King called 'the content of their character'. By extension, social equality is unjust because it treats unequal individuals equally.” "Political Ideologies" by Andrew Heywood (2003)
damn mouse doesn't work like it used to.
Thanks, natural, for the reply. It has been historically enlightening.
Natural, I do agree that science daily and other sources are not so scientific as they should be, but that is their only flaw. They bring a vast wealth of knowledge that noone would have access to if they were not around. 99%+ of science magazines and websites require you to pay them significant funds in order to read the material they provide. Whereas sites like science daily use advertising revenue. Therefore I blame the journals for hoarding the knowledge, and requiring places like science daily to run sub-par articles just to get enough revenue to make a profit. It's the market law in full force: You can get it fast, cheap, or in good condition. Pick two.
Enlightened Atheist, Gaming God.
Good points all around. At the end of the day, I'm happier having Science Daily around vs. not having it around. They do at least provide some useful value. I'm just disappointed with the quality of it. Maybe I'm being nit-picky, but to me it seems important enough to complain about occasionally.
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