Posted on May 29, 2010 by Afarensis, FCD
Consider the changing morphospace within the stem group of a phylum when it is traced back through successively earlier nodes from the ancestor of the crown group (the crown ancestor) to its last common ancestor with a sister phylum. The crown synapomorphies are lost immediately. Some stem-group branches may be quite diverse, and their derived features may be so morphologically striking that in Linnean classification these branches would rank as extinct classes or orders of the phylum, ranks they can not be assigned in cladistic classifications. Proceeding toward the last common ancestor with a sister phylum, the constellation of features continue to erode. Eventually the morphologies at the nodes on the main line toward the common ancestor become dominated by features that are plesiomorphic. Finally, unique features of the phylum can no longer be recognized, and by definition the phylum is no longer present.
The above quote occurs on page thirty-one of Valentine’s book On the Origin of Phyla. Earlier Valentine had said:
Stem-group taxa expand the morphological features and, usually, the morphological disparity of a phylum beyond that of a crown group, while at the same time they lack crown-group synapomorphies.
This has some interesting implications for primate and human evolution. To see how this plays out in primate evolution you should read this post by Hawks. I had just finished reading Valentine’s book when Berger announced Australopithecus sebida and Curnoe announced Homo gautengensis. Some anthropologists (Clarke, for example) have long thought there were more than several species of australopithecine in South Africa and the same can be said for early Homo. Although Valentine was referring specifically to phyla above, the basic ideas in the above quotes can be applied to any crown group and stem group(s) – collectively known as a total group. More on this later.
Filed under: Australopithecus, Homo gautengensis, Paleoanthropology | Tagged: Australopithecines, Homo gautengensis | Comments Off
Posted on May 27, 2010 by Afarensis, FCD
Turns out the Designer isn’t Jehovah, or even a more interesting deity like Aphrodite or Thor, rather the designer is the lowly termite at least in Kenya anyway.
Filed under: Biology, Ecology | 2 Comments »
Posted on May 19, 2010 by Afarensis, FCD
There are a number of papers with datasets in the paleoanthropological literature that I am wanting to play around with but I can’t afford PAUP. So I am throwing the question to my readers…Other than PAUP are there any good phylogenetic programs out there? Programs that can be used for continuous and discrete characters? Preferably free?
Filed under: Administrative | 5 Comments »
Posted on May 18, 2010 by Afarensis, FCD
John Lynch mentions that it has been a year since he left ScienceBlogs. It has been a year for me as well, my last post at ScienceBlogs being on May 7th, 2009. I can’t say that I miss being there and most of the ScienceBloggers that I read regularly have since moved on – there are a few still lingering though. I have gotten over 100,000 hits in the past year with my best day being 10/27/09 with my letter to Alan Grayson. In looking at my stats one of the more interesting things that jumps out is that I have incoming links from a wider, more diverse group of blogs than when I was at ScienceBlogs. Which is cool…
Filed under: Administrative | 3 Comments »
Posted on May 17, 2010 by Afarensis, FCD
This is tragic:
Members of the Instituto Butantan said the nearly 100-year-old collection lost in Saturday’s fire included almost 80,000 snakes and several thousand specimens of spiders and scorpions. The specimens were used to study evolution and provided information on how to avert extinctions, said institute director Otavio Mercadante.
“The entire collection was lost, the biggest collection of snakes in the world,” curator Francisco Franco told Globo TV and other local media. “It’s a loss to humanity.”
Filed under: Biology | Comments Off
Posted on May 14, 2010 by Afarensis, FCD
Sci ence Daily mentions this article in connection with forensic anthropology. This is the gist of the article (from Science Daily):
The researchers collected craniofacial measurements from the remains of children between the ages of 14 and 16. The researchers then ran the data through modeling software and additional statistical analyses to determine whether children differ significantly from adults in terms of the craniofacial markers that identify a given population.
In addition to forensic applications, the findings also represent a breakthrough for physical anthropologists studying past civilizations. Because craniofacial characteristics are used to examine differences between populations, these findings can help anthropologists advance our understanding of how populations have moved or changed over time. The study shows that anthropologists can now use the remains of children to help get a snapshot of what the population looked like in a specific area — they are no longer limited to using the craniofacial remains of adults.
Can someone send me a copy of the Journal of Craniofacial Surgery article – link above.
Filed under: Uncategorized | 2 Comments »
Posted on May 12, 2010 by Afarensis, FCD
Science humor rules!
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