Posted on 08/15/2007 2:51:14 PM PDT by blam
Not breeding obvious in splits of human evolution
Simon Grose
15 August 2007
ABOUT 353,000 babies will be born into the world today, about 700 of them in Australia. Same as yesterday and same as tomorrow. Many of their parents will worry about being able to properly feed them, or whether they may have contracted HIV in the womb. Whatever circumstances today's new children and their families face, every birth evokes a degree of hope. Firstly, that the baby is fit and well. Beyond that, a myriad of hopes can be evoked to lead their nation, to be rich, beautiful, a sporting champion, and so on. But no parents cradle their newborn child and wonder if they have spawned a new species. For the estimated 150,000-200,000 years that our species has trod the globe, its members have made billions of babies and none have broken the Homo sapiens mould.
Within that mould there has been much genetic variation. Some individuals are much taller or shorter than normal, others markedly more or less intelligent than normal, and people with Down syndrome carry one more chromosome than is normal. But none of these variations are sufficient to define them as other than Homo sapiens.
It happens though. The uncountable millions of species of plants and animals living now or in the past were all the product of a genetic shift from their forebears. For Homo sapiens, the fossil record contains evidence of at least 14 species who preceded us on the evolutionary pathway over the past 4.6million years, either as direct ancestors or as relatives of those ancestors. Fossil finds from the banks of Lake Turkana in Kenya, revealed in the science journal Nature last week, opened a window on to this process, as well as exposing different interpretations by experts and how the media can be led to exaggerate the implications of scientific research.
"The discovery of two fossils has challenged the belief that our ancestors Homo erectus evolved from Homo habilis, according to a new study [that] suggests that the two species may in fact have co-existed for some 50,000 years in East Africa," Agence France-Presse said in a report indicative of coverage around the world.
However, towards the end of the Nature report, the authors acknowledge that "it is nonetheless possible that H.erectus evolved from H.habilis elsewhere, and that the Turkana basin was a region of secondary contact".
For Professor Colin Groves, of the Australian National University's School of Archaeology and Anthropology, the findings are interesting but untoward. "It just shows that habilis was there till much later than we thought and reinforces that primitive species live alongside their descendants," he said yesterday. "I don't know whey they puffed it so much."
Nor do the Nature paper authors deal with the fact that the fossil they classify as Homo erectus would be classified by others including Groves as Homo ergaster.
This highlights ongoing differences over classification of ancient species in the fascinating area of human evolutionary theory. Whereas Groves and others see sufficient variation between fossils to classify Homo ergaster and Homo erectus as separate species, others see sufficient similarities to classify them both as Homo erectus.
For those who classify them separately, Homo ergaster existed from 1.8 to 1.2million years ago and Homo erectus branched off from this line about 1.3million years ago, possibly surviving till as late as just 100,000 years ago. For the other camp, it was the same species all along. If the first theory is correct, Homo erectus was not a direct ancestor of ours because our line branched off from Homo ergaster after Homo erectus branched off. If the second is true, Homo erectus was one of our direct ancestors.
It's all a matter of degree because the longer a species survives, the more it changes. Although, in his judgment, Homo erectus existed as a species for about 700,000 years less than the Nature authors believe, Groves says "the end ones certainly are strikingly different from the early ones", particularly in the larger size of their brains. This process of evolution within a species is termed anagenesis.
The more dramatic event, when a species divides into two, is known as cladogenesis. For this to occur, a group of individuals must become geographically isolated. "When a small part of a lineage becomes separate from the rest, changes occur very quickly in that small group until finally new characteristics become fixed," Groves said.
Isolation is necessary for cladogenesis and time. The fossil record between us and what most believe to be our immediate ancestor, Homo heidelbergensis, includes two dated at 195,000 years ago of which Groves says one has several characteristics akin to Homo sapiens. These individuals were single genetic steps in a process that took tens of thousands of years, triggered by isolation of a core group.
So new parents should not expect their babies to be anything other than Homo sapiens. And with about 200,000 more births than deaths each day around the world, there is a diminishing likelihood that any group of Homo sapiens will become sufficiently isolated to kick-start a new breed.
Simon Grose writes on science and technology.
“Congratulations, you’ve almost figured out why evolution is just another form of junk science. The whole thing is driven by information..”
Thats pretty much it in a nutshell. Information. You just can’t trust information.
I haven't seen anyone on this thread mention PE. In fact, I don't see what it has to do with anything in this article, or in blam's post. Why are you bringing it up?
The last paragraph of the article does in fact refer to the basic idea of PE.
Nope, nothing about punk eek here. The author's talking about the potential (or lack there of) for future allopatric speciation, which can happen either under punk eek or gradualism.
You should read more about the various mechanisms of speciation (allopatric, sympoatric, parapatric, and heteropatric). It's fascinating.
Nope, nothing about punk eek here....
You should read more about...
Really? When was the last time you bred with an individual from the deepest African rain forests or the Kalahari Desert?
Cross-breeding is insufficient to explain speciation because the first two speciation events of life (i.e. abiogenesis and then the 2nd species to form) had no such cross-breeding options.
Further, the author of this article is claiming that mutations and new species are more possible with 10,000 pre-humans than with 6 billion modern humans.
That dog won’t hunt. For that matter, even the “isolation leads to speciation” theory fails to explain why pigeons in Australia are the same as pigeons in New York City or London. It’s not like they’ve been flying across oceans to breed for the past million years...
But it doesn't. There are perfect examples of speciation from isolation still living -- with all of the intermediate forms (transitionals, or "missing links") still in place!
Just google "ring species!"
Ring species provide unusual and valuable situations in which we can observe two species and the intermediate forms connecting them. In a ring species:
- A ring of populations encircles an area of unsuitable habitat.
- At one location in the ring of populations, two distinct forms coexist without interbreeding, and hence are different species.
- Around the rest of the ring, the traits of one of these species change gradually, through intermediate populations, into the traits of the second species.
A ring species, therefore, is a ring of populations in which there is only one place where two distinct species meet. Ernst Mayr called ring species "the perfect demonstration of speciation" because they show a range of intermediate forms between two species. They allow us to use variation in space to infer how changes occurred over time. This approach is especially powerful when we can reconstruct the biogeographical history of a ring species, as has been done in two cases. Source
Two different colors of the same salamander or warbler do not make for different species any more than two different colors of humans makes for two different species.
Now we know who bred with the offspring of Adam and Eve.
Please read the information I posted and linked.
It is not the color of the salamanders but their inability to interbreed at the ends of the ring!
That is the definition of a species.
Biologists have *two* mutually exclusive definitions of speciations: any change or the inability to cross-breed.
As for inability, there is a grand difference between lack of desire from that of lack of capability.
That the same salamander “can’t” breed with the same salamander but of a different color is preposterous. That one color salamander wouldn’t *want* to breed with the same species in a different color is far more plausible.
Some white guys don’t fancy black girls. No big deal. But they *could* breed with black girls. Big difference between “don’t want to” from that of “can’t do it physically.”
For that matter, even the “isolation leads to speciation” theory fails...I pointed out examples where that is not correct.
Your counter-arguments (i.e., "there is a grand difference between lack of desire from that of lack of capability") do not change the fact that interbreeding does not occur at the endpoints of ring species.
In these cases, isolation has indeed led to speciation. No theory needed, just observation.
Junk science or not, it is pointless. Many years ago, I asked a Muslim friend of mine what he thought about evolution. He shrugged. What does it matter?
We are what we are now by God’s will. (he did not use the word Allah). But the article makes a good point. We’re not going to change. That being said, I don’t think he acknowledges that the evidence shows that species, even microorganisms, are more resistant to change that Darwin ever dreamed. Regression to the norm seems to be the rule.
Isolation does *not* lead to speciation. If it did, then pigeons in New York would be different from pigeons in Australia.
And “ring species” are no such thing...just the same species in different colors.
More than that, it's a rule that never gets violated. The fruit fly experiments proved that.
You obviously have don't have the foggiest idea of what punctuated equilibrium is.
You obviously have don't have the foggiest idea of what punctuated equilibrium is.
So now they teach evolutionism including the ****ed attitudes in econ courses??
PE was an attempt to get around at least three of what Gould and several of his compatriots viewed as the big problems of standard Darwinism, i.e. the lack of intermediate fossils, the Haldane dilemma, and the fact that evolutionary dogma was preventing palaeontologists from publishing papers which dealt with questions of stasis in the fossil record.
"Allopatric speciation" is precisely the thing which the Haldane dilemma forbids. A reader would therefore be correct to assume ( as I did and you didn't know enough to) that the final paragraph of the article above referred to the possibility of small groups being isolated as Gould and others describe (i.e. ala PE).
Are there any other unrelated topics which the econ degree makes you an automatic expert at?
A pigeon is just a pigeon, and it is well known that they are all exactly alike. (Except, of course, when they're not: Dove & Pigeon Species Listing)
And “ring species” are no such thing...just the same species in different colors.
You should publish this. You'll be famous.
You should be a comedian. You’ll get just as many laughs...
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