Anthropology.net

Another PNAS study to share with y’all, this time I caught the announcement via ScienceNOW. ScienceNOW says the paper is out today, but I can’t find it. Go figure. So all I got to run with is this news report.

The authors of this paper are Adam Gordon, Lisa Nevell, and Bernard Wood. They compared the size and shape of other hominid skulls with that of Homo floresiensis. They conclude that LB1,

“from the island of Flores is unlikely to be a shrunken or diseased Homo sapiens, as some have argued, and that its ancestry may instead trace back to ancient Homo species in Africa.”

Two weeks ago we read a very flawed article that concluded Homo floresiensis was nothing more than a bunch of endocrine-ly challenged modern humans. There’s been a so much back and forthing on whether or not Homo floresiensis is a unique species that is has become tiresome to even keep up with the arguments. Sometimes it feels like ego is at more at stake here than really figuring out human evolution.

This new study seems to want to simplify things. From the news article,

“The researchers gathered published data on six measurements of skull shape, such as the height of the cranium and the forward jut of the jaw, on 2524 modern humans, 30 ancient hominids of various species, and the hobbit. Statistical analysis showed that the hobbit skull most resembled H. erectus skulls from Africa and Dmanisi, Georgia, dating as far back as 1.7 million years ago. Then, because the skull’s tiny size presumably influences its shape in certain ways, the researchers did a second analysis considering the effects of scale–in effect asking what type of hominid, if shrunk to hobbit size, would best match LB1. In this part of the study, LB1 most resembled African H. habilis, the most primitive and small-brained species of our genus, also dated to about 1.7 million years ago.

“This is particularly exciting because … it suggests that we really do have a hominin lineage that split off from our own as much as 1.7 million years ago, yet persisted up until the time when modern humans started peopling the Americas,” says Gordon.”

To recap on some osteological goodness, the six measurements are as follows:

1. Glabella to Opisthocranion, a measurement of the maximum length of the skull. That’s from the front to the back of the skull.
2. Basion to Bregma, a measurement of the of the maximum height of the skull. That’s from the base to the very tip top point of the skull.
3. Euryon to Euryon, a measurement of the maximum breadth of the skull. That’s from one side to the other side.
4. Nasion to Basion, a measurement of the length of the base of the skull.
5. Basion to Prosthion, a measurement of the distance between the base of the skull to the tip of the maxilla (upper jaw).
6. Biasterionic breadth, a measurement I haven’t heard of but looks like it is the width of the base of the skull.

I’m gathering that the authors took these multiple measurements and did a phylogenetic analysis. I am getting this from what was indicated in the above excerpt, they compared a lot of modern humans, fewer hominids of various species, and the hobbit. I don’t have the article to confirm this methodology, but I can only assume that is what they did to figure out LB1 is similar to Africa and Dmanisi Homo erectus, even H. habilis in some regards, based off of the measurements.

But, if you have read this paper, “Remains of Homo erectus from Bouri, Middle Awash, Ethiopia,” you should know how reconstructing phylogeny with cladistic analysis between early Homo species is hard and rather inconclusive. We know general trends and large scale similarities and differences, but when it gets to nitty gritty things, the paltry calvarial evidence for big differences between the African and Asian fossils make it really difficult to say Asian Homo erectus was that much different from African Homo erectus. Instead, it is much safer to say that Homo erectus existence spanned large time frames. And that even with a 1.2 million year old difference in time, Homo erectus from Africa to Asia was pretty much the same thing.

For that reason, I wonder how LB1 can be like Homo erectus… especially a really old African erectus as indicated in the report? Above, I put a lateral view of LB1 as well as a lateral view of a Dmanisi Homo erectus (D2700), one that the authors say LB1 resembles. Just by eyeballing the differences between the two skulls we can see that D2700 is much longer, and has a big difference in the basion to prosthion length.

If we take into consideration the works of Asfaw et al., there aren’t many differences between African and Asian Homo erectus that can be figured out thru cladistics. And Asian Homo erectus persists in the record into much more recent times. So, why isn’t LB1 related to an Asian Homo erectus? They should be synonymous, no? What is particularly African erectus about LB1?

Furthermore, how can a tiny hominid like LB1, with a brain half the size of Homo erectus and an antiquity of only 18,000 years old, be compared to one of the root species of Homo? Some of the earliest Homo had brain sizes of 900 or so cc. LB1 had a brain size of 440 cc. Big difference here folk. The news article reports that they ‘shrunk’ the proportions of other early Homo skulls down to LB1′s size to compare. Is that even a valid way to compare? The very fact that LB1 is distinct is its size, so scaling down comparative measurements seems flawed because we’re comparing apples to oranges watermelons here. You can’t just scale down a watermelon down to the size of an apple and begin to start concluding their similar.

I’m not alone scratching my head over this. Christoph Zollikofer, also has some problems with this cladistic approach. He says the six measurements aren’t enough to

“capture the complexities of skull shape, a concern shared by others. In his view, this kind of analysis might cluster together skulls that are actually distinct. Depending on the species included, says Zollikofer, the approach could end up finding similarities between LB1 and chimpanzees.”

I guess we all gotta wait until PNAS puts out this paper.

Asfaw, B., Gilbert, W.H., Beyene, Y., Hart, W.K., Renne, P.R., WoldeGabriel, G., Vrba, E.S., White, T.D. (2002). Remains of Homo erectus from Bouri, Middle Awash, Ethiopia. Nature, 416(6878), 317-320. DOI: 10.1038/416317a

Today’s early issue of PNAS includes a paper by Tim Weaver, Charles Roseman and Chris Stringer who revisit the chance or natural selection issue in regards to Neandertal and modern human speciation. You may remember they published a paper in August of 2007, in which they basically concluded that natural selection really didn’t have anything to do with why Neandertals are so morphologically different. According to these older results, there really hasn’t been a real benefit to their really robust skulls with large noses, rather those traits just sprung about by chance. That goes against a lot of adaptionists hypotheses that proposed Neandertal robusticity has been selected in response to the cold and harsh environment they lived in.

The new paper is titled, “Close correspondence between quantitative- and molecular-genetic divergence times for Neandertals and modern humans,” and Weaver et al. apply their older data set of, “37 standard cranial measurements collected on 2,524 modern humans from 30 globally distributed populations and 20 Neandertal specimens” to some improved algorithms. The abstract indicates they built upon the older model, that used changes in microsatellites as a framework for understanding selection versus random genetic drift. With this ‘clock’ of sorts, they were actually able to present a divergence time of neutrally evolving morphological measurements.

I don’t have access to the PNAS paper just yet. For some odd reason my institution’s library access is always a day behind, so if anyone would be so kind enough to email me the paper, nevermind I got it. Anyways, I’ll be more than happy to figure out how they were able to use a ‘reverse’ molecular clock. See usually molecular clocks are calibrated on the fossil record, but in this situation it seems like it is the opposite. It seems the authors were able to figure out a clock for random genetic drift and correlate that to morphological traits.

They were able to pluck out two dates, which differ by around 120,000 years because of difference between ‘within-population variation.’ The low end of the speciation time for Neandertals is at 311,000 years ago with a high end at 435,000. The confidence intervals for the 311,000 year old date are pretty gnarly, but in general this date is beginning to fall much more in line with the genetic data. Anyways it looks like a good paper, but I really don’t know the details, if someone out there wants to send me the PDF, please do. Got it.

WEAVER, T., ROSEMAN, C., STRINGER, C. (2007). Were neandertal and modern human cranial differences produced by natural selection or genetic drift?. Journal of Human Evolution, 53(2), 135-145. DOI: 10.1016/j.jhevol.2007.03.001

Michael Callahan of Ambient Corp. in Champaign, Ill. and the University of Illinois has recently introduced The Audeo, a thought-to-speech interfacing device which acquires and converts neurological signals into vocalizations. The device allows users to communicate with a computer much in the way voice recognition software does. However, instead of encrypting wave patterns detected in recorded utterances, The Audeo acquires and discerns individual words from neurological signals produced by the intent to vocalize.

The Audeo is being developed to create a human-computer interface for communication without the need of physical motor control or speech production. Using signal processing, unpronounced speech representing the thought of the mind can be translated from intercepted neurological signals. By interfacing near the source of vocal production, the Audeo has the potential to restore communication to people who are unable to speak. The proposed solution is a featherweight wireless device resting over the vocal cords capable of transmitting neurological information from the brain. Using data analysis, this information can be processed into synthesized speech or a menu selection capable of conveying the basic necessities of human life.

Callahan suggests possible applications of the technology, including wheelchair control for the disabled and thought-to-speech conversion for patients with ALS (amyotrophic lateral sclerosis) who lose the ability to speak over time. Demonstrations of the device can be found in the media section of The Audeo’s website as well as at the Texas Instruments Developer’s Conference Keynote. Although the prospect of retaining voices for ALS patients sounds promising, there may be a down side. If such technology were cheap and efficient, would this bear implications on sign language? As Standard American English (and other prestige dialects) continues to be commodified on 24-hour global news networks, endangering small languages, could the prospect of a new voice place signed languages in danger?