MI weekly selection #8

Location of Xaltocan in Aztec times | Credit: Xaltocan Acheological Project
Location of Xaltocan in Aztec times | Credit: Xaltocan Archeological Project

Your molar roots are leftovers from Homo erectus

Adult human molar roots form for at least a year before erupting from the gum line, according to research published in the journal PLoS ONE. Researchers say the majority of the formation of teeth has evolved to keep up with longer human lifespans, except for the adult molar, which appears to develop at the same speed now as it did with the Homo erectus, our early ancestors.

New Scientist

Dean MC, Cole TJ (2013) Human Life History Evolution Explains Dissociation between the Timing of Tooth Eruption and Peak Rates of Root Growth. PLoS ONE 8(1): e54534. DOI:10.1371/journal.pone.0054534

Thriving community of microbes found high in Earth’s atmosphere

A large number of microorganisms have been discovered high in Earth’s atmosphere, suggesting that life above Earth’s surface is thriving and ever-changing. While some microbes appear to be just passing through, others appear to survive by breaking down organic chemicals in the sky, according to findings published in the journal Proceedings of the National Academy of Sciences. “There are a few species that are quite abundant,” said Kostas Konstantinidis, an environmental microbiologist and the study’s co-author. “That becomes very interesting — what are all these cells doing up there, and how do they survive?”

Our Amazing Planet

Natasha DeLeon-Rodrigueza, Terry L. Lathemb, Luis M. Rodriguez-Ra, James M. Barazeshc, Bruce E. Andersond, Andreas J. Beyersdorfd, Luke D. Ziembad, Michael Berginb, Athanasios Nenesb,e,1, and Konstantinos T. Konstantinidis (2013) PNAS DOI: 10.1073/pnas.1212089110

Electricity might play a role in growing iron-eating bacteria

A new cultivation method using electricity could help scientists reproduce iron-oxidizing bacteria in the lab. The bacteria “eats” the electrons in iron, causing rust, and has been characteristically difficult to grow in a lab. Electrochemical cultivation is a “new way to cultivate a microorganism that’s been very difficult to study. These organisms can synthesize everything they need using only electricity.

Mother Nature Network

Zarath M. Summers, Jeffrey A. Gralnick, Daniel R. Bond (2013) Cultivation of an Obligate Fe(II)-Oxidizing Lithoautotrophic Bacterium Using Electrodes mBio DOI: 10.1128/​mBio.00420-12

Brain capable of “retroactive editing” to retain conscious thoughts

The human brain can retroactively adjust conscious experiences to retain memory, a study found, contradicting a long-believed theory that the brain processes information sequentially before consciously experiencing it. Retroactive editing can explain why someone can recall something without remembering ever hearing it in the first place.


Claire Sergent, Valentin Wyart, Mariana Babo-Rebelo, Laurent Cohen, Lionel Naccache, Catherine Tallon-Baudry (2012) Cueing Attention after the Stimulus Is Gone Can Retrospectively Trigger Conscious Perception Current Biology DOI: 10.1016/j.cub.2012.11.047

Aztec coup of Mexican city led to assimilation, not abandonment

A DNA analysis of remains found in Mexico’s ancient city of Xaltocan reveals fundamental differences between the people before and after the arrival of Aztec conquerors, helping to answer the mystery of whether the city’s residents abandoned the city or simply assimilated with the more powerful kingdom. The study, published in the American Journal of Physical Anthropology, supports the theory that a major demographic shift occurred when the Aztecs arrived in 1435, rather than the notion that the city was abandoned en masse in 1395.


Jaime Mata-Míguez, Lisa Overholtzer, Enrique Rodríguez-Alegría, Brian M. Kemp, Deborah A. Bolnick (2013) The genetic impact of aztec imperialism: Ancient mitochondrial DNA evidence from Xaltocan, Mexico American Journal of Physical Anthropology DOI: 10.1002/ajpa.22152

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