The context does not contradict that statement. Every single measure used on every other animal would at minimum place humans in several subspecies. But we do not apply the same standards to ourselves for political reasons.
> Thus, population genetic, phylogenetic, and network analyses of nuclear sequences demonstrate that the giraffe is genetically well structured into four distinct species. This is consistent with divergence times of 1.25 to 2 million years ago (mya) among the four clusters (Figure 3C).
That genetic isolation is 100x longer than the human migration to the Americas. It's also 10x longer than the time to "Mitochondrial Eve" and about 8x longer than to "Y-chromosomal Adam".
Humans do not meet the phylogenetic criteria which justifies the use of "subspecies". See http://www.nature.com/ng/journal/v36/n11s/full/ng1455.html and many others. Quoting that reference:
> Modern human genetic variation does not structure into phylogenetic subspecies (geographical 'races'), nor do the taxa from the most common racial classifications of classical anthropology qualify as 'races' (Box 1). The social or ethnoancestral groups of the US and Latin America are not 'races', and it has not been demonstrated that any human breeding population is sufficiently divergent to be taxonomically recognized by the standards of modern molecular systematics. These observations are not to be taken as statements against doing research on demographic groups or populations. They only support a brief for linguistic precision and careful descriptions of groups under study. Terms and labels have qualitative implications.
There is no scientific basis for that claim. Many other animals have diverged less, in less time and are still separate subspecies.
>African > Eurasia had regular exchanges as they where within relatively short walking distances.
Interbreeding does not mean subspecies don't exist. Coyotes and wolves are totally separate species and they interbreed. This does not make them the same species, much less the same subspecies. Or the very example given in the article: polar bears and brown bears. Separate species, overlapping geographical regions, crossbreeding occurs in the overlap. Or again from the article example: giraffes.
Also note they talk about the genetic distance, but the genetic distance between a west african and an australian aboriginal is greater than the difference between wolves and dogs, which are subspecies. Again, by all measures we use for wild animals, humans consist of several subspecies at least.
> A comparison of the nuclear genome of polar bears with that of brown bears revealed a different pattern, the two forming genetically distinct clades that diverged approximately 603,000 years ago,[25] although the latest research is based on analysis of the complete genomes (rather than just the mitochondria or partial nuclear genomes) of polar and brown bears, and establishes the divergence of polar and brown bears at 400,000 years ago.
> ... However, because neither species can survive long in the other's ecological niche, and because they have different morphology, metabolism, social and feeding behaviours, and other phenotypic characteristics, the two bears are generally classified as separate species.[29]
Ed: I don't disagree with what you're saying, I just don't think it's relevant to discussions of DNA. We can call Pluto a potato, does not change anything. As to classification the trend is clearly to call them the same species we just need to let the old scientists die off ;)
So, in theory you can have genetically compatible separate species as soon as they are no longer capable of interbreeding. However, as Humans and Brown bares are both biologically capable of interbreeding and live in such a manner that the do interbreed they don't fit that definition. Temporary barriers are not necessarily enough as they may exchange DNA in the future.
PS: Ring species are considered a single species because a mutation can start at one end and given time make it's way around the ring. Thus they are a single pool that can and will exchange DNA.
No, that was one long discredited idea of species. It has not been used in decades. Why are you so insistent on pushing this false claim that brown bears and polar bears are the same species? Look it up, they are not. One is Ursus arctos and the other is Ursus maritimus. There is no ambiguity or dispute.
That analogy is not useful at all. Continents are not biological organisms.
>Genetically brown and polar bears can and in reality often do interbreed producing viable offspring and exchanging genetic information between populations
And yet they are separate species. Just like the 4 separate species of giraffe the article is about, which can and do all interbreed. The concept of species is in no way reliant on an inability to produce fertile offspring.
At most you can say brown and polar bears are "generally classified as separate species" But, there really is debate on this topic.
Perhaps even less.
http://www.andrewcollins.com/page/articles/romanbust.htm
There was at least some contact between North America and Europe, close to 2K years ago.
For substantial periods of the past 50k years, Australia, Indonesia, and the South Indian subcontinent were joined or nearly so, due to lower sea levels. Much of the area remains quite shallow. At about 15-20kya:
http://www.global-greenhouse-warming.com/ice-ages-and-sea-le...
https://upload.wikimedia.org/wikipedia/commons/1/19/CLIMAP.j...
Australasia[edit] The Australian mainland, New Guinea, Tasmania and many smaller islands comprised a single land mass. This continent is now referred to sometimes as Sahul. Between Sahul and Sundaland – a peninsula of South East Asia that comprised present-day Malaysia and western and northern Indonesia – there remained an archipelago of islands known as Wallacea. The water gaps between these islands, Sahul and Sundaland were considerably narrower and fewer in number.
Thus, a 50 mile gap between Asia and the United states was likely crossed a few times.
There where early tool across Afro-Eurasia as far back as 1.7 to 2.6 million years. Early human ancestors may have maintained separate populations spreading genetic mutations between them with occasional waves of migration displacing existing populations. Supporting the first idea is the wide range of habitat giving advantages to prior populations who are better able to cope with existing conditions. http://www.nature.com/news/teeth-from-china-reveal-early-hum...
There really does not seem to be much evidence to tell one way or another.
However, if you accept the first habitation probably did not leave a lot of clear evidence some date prior to 46,000 years seems likely.
While time is a factor 14,000 is more than enough for humans to speciate, the reason why this hasn't happened to humans is something that is actually a subject of research today.
And this isn't because birds are special but because they tend to migrate, in other cases natural or manmade barriers that split a species into distinct groups have also causes speciation after only a handful of generations. Besides birds where it's common due to migration patterns "man caused" rapid speciation has also been observed in rodents (squirrels/mice) and various types of fish.
http://evolution.berkeley.edu/evolibrary/news/100201_speciat...
You do not need a 1000 generations to speciate.
The second description concerns a pairing between two hybrids which started a new lineage. It uses the term "lineage" instead of saying there is a new species.
> These two examples make it clear that the division between species is not a black-and-white issue. Rather, speciation occurs as many different sorts of traits (physical, behavioral, and genetic) diverge from one another along a continuum. Because of this, biologists sometimes disagree about where to draw the line between incipient species — about when a division has become deep enough to warrant a new species name. Whatever we choose to call them, these two cases clearly illustrate how a lineage can split and begin to make its way down two separate evolutionary paths.
Regarding ring species, https://en.wikipedia.org/wiki/Ring_species says "Currently, there are four known forms of life that appear to match the definition of a ring species". Frankly, I thought there were more. It would suggest that birds don't tend to rapidly form ring species.
> You do not need a 1000 generations to speciate.
Are either of those two cases described in the literature as a new species, or are they given as a subspecies, or variant, or fertile hybrid, or some other term?
Also don't rely on wikipedia for accurate information about many subjects, it's ok but it's far from perfect or being technically correct.
As for the rest of your argument that's semantics and it clearly misses the conclusion of that article:
"While we can't know the fates of these lineages, directly observing such divergences in real time highlights the fact that we don't always need to look into the distant past or far off future to find examples of speciation in action. Evolution is occurring all around us. We just need to learn where and how to look for it."
We have examples of speciation and divergence in real time over a handful of generations, a species at the end is a group which is capable and practices interbreeding amongst its members but does not breed with others.
The PNAS paper for the first event does not give a binomial. It says:
> We treat the endogamous group as an incipient species because it has been reproductively isolated from sympatric G. fortis for three generations and possibly longer.
I was not aware that this was the accepted common definition of a species.
The second also does not give a binomial. It describes a method to "initiate evolution of reproductive isolation among sympatric populations".
Is that enough to say that there is a new species? If so, I was not aware that the threshold for a species definition was so sensitive.