A number of items, ranging from paleontology and developmental genetics to osteology and primatology caught my attention this week.
First up, and interesting study in Nature on jawless fish from China. Here is the abstract:
Most living vertebrates are jawed vertebrates (gnathostomes), and the living jawless vertebrates (cyclostomes), hagfishes and lampreys, provide scarce information about the profound reorganization of the vertebrate skull during the evolutionary origin of jaws1–9. The extinct bony jawless vertebrates, or ‘ostracoderms’, are regarded as precursors of jawed vertebrates and provide insight into this formative
episode in vertebrate evolution8–14. Here, using synchrotron radiation X-ray tomography15,16, we describe the cranial anatomy of galeaspids, a 435–370-million-year-old ‘ostracoderm’ group from China and Vietnam17. The paired nasal sacs of galeaspids are located anterolaterally in the braincase, and the hypophyseal duct opens anteriorly towards the oral cavity. These three structures (the paired nasal sacs and the hypophyseal duct) were thus already independent of each other, like in gnathostomes and unlike in cyclostomes and osteostracans (another ‘ostracoderm’ group), and therefore have the condition that current developmental models regard as prerequisites for the development of jaws1–3. This indicates that the reorganization of vertebrate cranial anatomy was not driven deterministically by the evolutionary origin of jaws but occurred stepwise, ultimately allowing the rostral growth of ectomesenchymethat now characterizes gnathostome head development1–3.
Next up, a study that looks at the evolution of regulatory genes during vertebrate evolution. From Science Daily:
The study, led by scientists at the University of California, Santa Cruz, and published this week in Science, focused on regulatory elements that orchestrate the activity of genes. They found three broad categories of evolutionary innovations in gene regulation that increased in frequency during different periods in vertebrate evolution. The first period, for example, was dominated by regulatory innovations affecting genes involved in embryonic development. These changes occurred during the period leading up to about 300 million years ago, when mammals split off from birds and reptiles.
On a related note, results the genome sequencing of the tammar wallaby has been published in Genome Biology. The study yielded some interesting insights into kangaroo life history – and how they hop.
A study in the AJPA looks at the developmental plasticity of the human jaw the study examined the development of the human jaw – from juvenile to adult – in two different populations with two different dietary patterns. From PhysOrg.Com:
The researchers precisely measured jaw bones from 63 members of the Point Hope population and 42 individuals from the Arikara population using an X-ray gun as well as calipers, and they used those measurements to extrapolate the proportions of the entire jaw. “The jaw bones were similar in children before they were old enough to start chewing, but different in adulthood, which implies that this divergence is likely a functional result of their diet and the use of their jaw, rather than genetics,” says Holmes.
On a related note a study in Biology Letters looks at the relationship between absolute latitude and human orbital volume. From PhysOrg.Com:
That the explanation is the need to compensate for low light levels at high latitudes is indicated by the fact that actual visual sharpness measured under natural daylight conditions is constant across latitudes, suggesting that the visual processing system has adapted to ambient light conditions as human populations have moved across the globe.
The study takes into account a number of potentially confounding effects, including the effect of phylogeny (the evolutionary links between different lineages of modern humans), the fact that humans living in the higher latitudes are physically bigger overall, and the possibility that eye socket volume was linked to cold weather (and the need to have more fat around the eyeball by way of insulation).
Finally, a study published in PNAS looks at how being separated from their mother affects baby rhesus macques. The study shows that the negative effects of maternal separation could still be seen three years after the separation.
Filed under: Interesting Science News |