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It's interesting to note that the fossil record shows an apparent overall reduction in the morphological variety and number of hominans in the million years or
by necolas 15y ago
It's interesting to note that the fossil record shows an apparent overall reduction in the morphological variety and number of hominans in the million years or so before present.
When we talk about Homo ergaster and Homo erectus it doesn't do justice to the significant variation among, and geographic distribution of, the fossils that are grouped under these species names. It's hard to know which variation can be accurately attributed to intra-species variation or sub-species or even separate species.
However, what is clear is that there is a great deal of variation in Africa, Asia, and Europe around the time of the "eretines". My feeling (back when I was a student) was that the archaeological evidence suggested an ongoing adaptive radiation of sorts, rather than the classic picture of a steady and relatively homoegeneous trajectory towards modern humans. But a lot of new research has been done since then that I'm not up to speed on.
Prior to the displacement and extinction of the remaining human forms there was already a reduction in the number and variation of Homo species. Even within our own species, there was much greater variation some 200-150kya.
There aren't any easy (accurate) answers to these sorts of questions, which is also why they are such fascinating areas of research. Understanding all the factors and events involved is very difficult with the type of information available.
You just have to look at the incredible lack of hominid (great ape) fossils for the last many million years of years to see know how difficult it can be to piece together an evolutionary history of a taxonomic group.
- bellaire 15y agoGreat post, more informative than the article. As far as I know, the adaptive radiation theory is now held as correct for hominids just as it is for every other group of species. The "classical" teleological viewpoint doesn't hold up to scrutiny for the reasons you cited.
- necolas 15y agoTeleology is something quite different. Not every period of evolution in a taxonomic branch is going to involve adaptive radiations. Although early human evolution is generally thought to have involved an adaptive radiation, by the time we get to 2mya a lot of the literature was assuming only 2-4 species existed over the next 2 million years.
- bellaire 15y agoTeleology was used somewhat tongue-in-cheek. The older literature was problematic because it aligned too neatly with anthropocentric ideas of goal-oriented evolution, and gave rise to nonsense objections like "Where is the missing link?" and "Why are apes still around?" I don't doubt the integrity of the scientists who were involved with the earlier literature, but in hindsight it looks an awful lot like a teleological bias.
- Florin_Andrei 15y ago> the incredible lack of hominid (great ape) fossils for the last many million years of years Why do you call it "incredible"?
- necolas 15y agoWell, maybe incredible isn't the best word. There are so few of them and it makes piecing together the evolution of modern Great Apes (particular over the last 10 million years) particularly difficult [1]. Perhaps their habitat was not conducive to fossilisation of remains. Don't really know enough about that area of research. But I'd guess that preservation bias is a factor. [1] http://afp.google.com/article/ALeqM5g-BDjcKrIh9YFbsqsJiky6m2g6Nw http://afp.google.com/article/ALeqM5g-BDjcKrIh9YFbsqsJiky6m2...
- stcredzero 15y agoThere aren't any easy (accurate) answers to these sorts of questions, which is also why they are such fascinating areas of research. Understanding all the factors and events involved is very difficult with the type of information available. Speciation is only something that can be determined after the fact, anyhow. Species are entities we use to discuss the combination of innumerable bits of historical happenstance. Our being the only human species left might be due to little more than luck.
- necolas 15y agoContingency could well be involved. But it's not particularly easy to decide what constitutes a separate species, even with extant organisms. The categorisation of fossils into separate species is probably not as interesting or important as trying to understand what can be deduced from the amount of variation between and within populations.
- stcredzero 15y agoReally, it's just convenient to have nouns with which to have those conversations.