What I really want to see is a complete genome sequence of early Homo sapiens, e.g., from a sample about as old as Vindija and Denisova. If anyone knows of any such sequencing efforts in the works, write in the comments, or drop me an e-mail.
DNA analysis of ancient remains to uncover origin mysteries
Griffith University leads search for human evolution
In collaboration with the Universities of Auckland, Copenhagen and New South Wales, the researchers will analyse human remains from continental and oceanic Asia and Australia using more powerful newly developed ancient DNA sequencing methods.
Chief Investigator Professor David Lambert from the School of Environment says understanding where the earliest people of Asia and continental Australia came from is critical to understanding modern human evolution.
"The recent sequencing of the Australian Aboriginal genome has identified two waves of human migration through Asia,'' he said.
"Aboriginal Australians descended from an early human dispersal into eastern Asia, possibly 62,000 to 75,000 years ago.
"This dispersal is separate from the one that gave rise to modern Asians 25,000 to 38,000 years ago, although there is evidence for hybridisation between them."
The researchers aim to identify descendent individuals from both lineages and detect historic patterns of interbreeding among these early people.
Professor Paul Tacon from Griffith University's Place, Evolution & Rock Art Heritage Unit said the research was a world-first study to attempt to recover human DNA sequences from more than 80 ancient human remains collected from a range of time points.
"We aim to identify the mitochondrial DNA lineage of each sample of human remains, the migration wave they represented and evidence of biological interactions, such as hybridisation with other groups.
"Although complete or draft genomes have been recovered from extinct species such as Neandertals and Woolly Mammoths, there are no existing populations of these species available for comparison.
"But an increasing number of complete human genomes in our study provide the foundation for this work."
Professor Tacon said the study was possible because of recent advances in second-generation DNA sequencing and parallel developments in DNA target capture technologies.
"These developments provide extraordinary new possibilities in the field of ancient human genomics."
The study is part of a $550,000 three-year Australian Research Council Linkage Grant.
Great news.
ReplyDeleteWe aim to identify the mitochondrial DNA lineage of each sample of human remains, the migration wave they represented and... ***evidence of biological interactions, such as hybridisation with other groups***.
ReplyDeleteAre they referring to inter-species hybridization here, or is "hybridisation" a term commonly used intra-species? Since they mentioned the Neanderthals, it sounds like they are in fact thinking about Denisovan and possibly other extinct hominid hybrid genes within the 'modern Human' population.
Should include Northeast Asians too. Isn't the frequency of Y-DNA C higher in Northeast Asian populations than SEA ones?
ReplyDelete"understanding where the earliest people of Asia and continental Australia came from is critical to understanding modern human evolution".
ReplyDeleteI agree 100% with that comment.
"Are they referring to inter-species hybridization here, or is 'hybridisation' a term commonly used intra-species?"
The term 'hybridisation' is often used for mixing of breeds of animals rather than specifically different species. I presume the researchers are primarily interested in hybrids within different groups of 'modern' humans in East and Southeast Asia. However I'm sure that if they find evidence for hybrid formation with earlier species they will follow that up.
"Should include Northeast Asians too. Isn't the frequency of Y-DNA C higher in Northeast Asian populations than SEA ones?"
True, but I am sure North Asians will eventually be included in the study. The phylogeny of Y-DNA C is very basic at present.
"The term 'hybridisation' is often used for mixing of breeds of animals rather than specifically different species. I presume the researchers are primarily interested in hybrids within different groups of 'modern' humans in East and Southeast Asia. However I'm sure that if they find evidence for hybrid formation with earlier species they will follow that up."
ReplyDeleteI was not aware that "hybridization" is a term used for different "breeds" of ~Human beings. I certainly wouldn't refer to any full-blooded Human being as a "hybrid".
If that's the case, any ~racially mixed person is a "hybrid" by your definition.
I've never heard of different "breeds" of say -- horses -- called "hybrids", either. Only mules (horse x donkey)...
"I was not aware that 'hybridization' is a term used for different 'breeds' of ~Human beings".
ReplyDeleteDifferent 'races' of humans are entirely equivalent to different breeds of domestic species.
"I certainly wouldn't refer to any full-blooded Human being as a 'hybrid'".
Ahh. But most humans are a mixture of at least several 'original' regional human varieties.
"If that's the case, any ~racially mixed person is a 'hybrid' by your definition".
Yes.
"I've never heard of different 'breeds' of say -- horses -- called 'hybrids', either. Only mules (horse x donkey)..."
Most farmers are aware of (and many use) 'hybrid vigour' where a cross between two pure breeds demonstrates increased production as compared to either pure breed.
"If that's the case, any ~racially mixed person is a 'hybrid' by your definition".
ReplyDeleteTerry: 'Yes.'
hy·brid (hbrd)
n.
1. Genetics The offspring of genetically dissimilar parents or stock, especially the offspring produced by breeding plants or animals of different varieties, species, or races.
So what you're doing is emphasizing the loosest and broadest definition of the term, by down-playing the "species" aspect of the definition.
Whereas, I find that aspect to be the most definitive and accurate of all. Because, it better serves to distinguish real ~subspecies from diverse parental stock.
A blend of different breeds (races) within a species, is not a ~subspecies. Yet Anthropologically speaking, Neanderthals and Denisovans ~are subspecies of Humans. (Just to get us back on topic).
To me, the question of ~species is more interesting and germaine than that of race.
"So what you're doing is emphasizing the loosest and broadest definition of the term, by down-playing the 'species' aspect of the definition".
ReplyDeleteNote, species is just one of the elements of genetic 'variety'. The definition says: 'genetically dissimilar parents or stock, especially the offspring produced by breeding plants or animals of different varieties, species, or races'. Surely that includes human races?
"it better serves to distinguish real ~subspecies from diverse parental stock".
Most 'species', by definition, will not form fertile hybrids.
"A blend of different breeds (races) within a species, is not a ~subspecies".
In certain conditions such a hybrid can form a new subspecies.
"Yet Anthropologically speaking, Neanderthals and Denisovans ~are subspecies of Humans. (Just to get us back on topic)".
And they could form hybrids with 'modern' humans, although as effectively as say, Chinese and Caucasian.
"To me, the question of ~species is more interesting and germaine than that of race".
Perhaps so, but the word 'hybrid' does not only encompass the crossing of separate species. In fact the definition of 'species' is actually a minefield.
Species: "2.A group subordinate to a genus and containing individuals agreeing in some common attributes and called by a common name."
ReplyDelete"Called by a common name" That alone should indicate that there is enough differentiation to classify them into separate special categories.
And differing numbers of ~chromosomes is another sign of differentiation.
Why is it a minefield? Politics?
"'Called by a common name' That alone should indicate that there is enough differentiation to classify them into separate special categories".
ReplyDeleteThat is absolutely insufficient to claim either separate or the same 'species'. Many species are called by different names in different places, and many different species are called by the same name in different places. The expression 'common attributes' is more adequate, but what are you going to call common attributes? The usual definition of 'species' is populations capable of producing fertile offspring. By that definition horses and donkeys are separate because the offspring are almost always infertile. But the same definition would make Denisovans and Neanderthals the same species as they obviously were able to produce fertile offspring.
"And differing numbers of ~chromosomes is another sign of differentiation".
That certainly doesn't apply in all cases. For example Przewalski's horse has an extra pair of chromosomes than do domestic horses, yet the two populations have no trouble forming fertile offspring:
http://en.wikipedia.org/wiki/Przewalski%27s_horse
"The karyotype of the domestic horse differs from that of Przewalski’s horse by an extra chromosome pair either because of the fission of domestic horse chromosome 5 in Przewalski’s horse or fusion of Przewalski’s horse chromosomes 23 and 24 in the domestic horse".
"Why is it a minefield? Politics?"
Generally not politics. The problem is that it is so often impossible to tell if two populations are different species or just different subspecies. Again the example of Przewalski’s horse:
"The taxonomic position is still debated, and some taxonomists treat Przewalski's horse as a species, Equus przewalskii".
But this is by no means the only pair of 'species' for which there is disagreement. Probably thousands of pairs.
"Why is it a minefield? Politics?"
ReplyDeleteI hope you can now see that the difference between 'species' encompasses the whole range between complete compatibility genetically, where hybrids are totally fertile, to complete incompatibility, where hybrids are unable to form.
An example of the first is the dabbling ducks, the mallard and, for example, the American black duck. Easily able to, and often does, form fertile hybrids. Cattle and yaks form hybrids where the female is fertile but the males are infertile. The horse and donkey form infertile hybrids. Horses and rhinoceros are completely unable to form hybrids although classified in the same family.
You asked elsewhere if there were any examples of a species evolving. Surely you must be able to accept that the dabbling ducks have evolved from a common ancestor, and presumably fairly recently. Cattle and Yak too presumably share an ancestor although in this case presumably some time ago. Horses and donkeys also appear to share a common ancestor, as do humans and chimpanzees.
And Dienekes has recently posted a recently discovered (or more exactly, proved) example of evolution within the bear family:
http://dienekes.blogspot.co.nz/2012/07/admixture-matters-for-polar-bears-too.html