Evolution

Many traits unique to humans are thought to have originated in the genus Homo between 2.4 and 1.8 million years ago in Africa.

What are the evolutionary factors that drove them?

A large brain, long legs, the ability to craft tools and prolonged maturation periods were all thought to have evolved together at the start of the Homo lineage as African grasslands expanded and Earth's climate became cooler and drier. However, new climate and fossil evidence analyzed by a team of researchers suggests that these traits did not arise as a single package. Rather, several key ingredients once thought to define Homo evolved in earlier Australopithecus ancestors between 3 and 4 million years ago, while others emerged significantly later.


The dominant hypothesis for the reason that northern Europeans developed light skin is that they needed to absorb more ultraviolet (UV) light to make more vitamin D, which is vital for healthy bones and immune function.

Not so, says a U.C. San Francisco dermatologist.  Peter Elias, MD, and colleagues write in Evolutionary Biology that changes in the skin's function as a barrier to the elements made a greater contribution than alterations in skin pigment in the ability of northern Europeans to make vitamin D. They write that genetic mutations compromising the skin's ability to serve as a barrier allowed fair-skinned Northern Europeans to populate latitudes where too little ultraviolet B (UVB) light for vitamin D production penetrates the atmosphere.


Old World monkeys have undergone a remarkable evolution in facial appearance as a way of avoiding interbreeding with closely related and geographically proximate species, according to a new paper which provides best evidence to-date for the role of visual cues as a barrier to breeding across species.

The researchers studied guenons—a group of more than two dozen species of monkeys indigenous to the forests of Central and West Africa. Many different species of guenons are often sympatric—they live in close proximity to each other, with multiple species often traveling, feeding, and sleeping side-by-side. Therefore interbreeding, which could result in afflicted infertile offspring, remains an unwelcome possibility. 


An electric discharge experiment simulates early Earth conditions using relatively simple starting materials. The reaction is ignited by a spark, simulating lightning, which was likely very common on the early Earth.

The 1958 reaction samples were analyzed by Parker and his current mentor, Facundo M. Fernández, a professor in the School of Chemistry and Biochemistry at Georgia Tech. They conducted liquid chromatography- and mass spectrometry-based analyses and found that the reaction samples from 1958 contained peptides. Scientists from NASA's Johnson Space Center and Goddard Space Flight Center were also involved in the analysis.


Writing about the weird soft-bodied fossils found in the Burgess Shale in the Canadian Rockies, paleontologist Stephen Jay Gould noted that of 25 initial body plans exhibited by the fossils, all but four were quickly eliminated.

If we rewound the tape, he asked, and cast the dice once more, would the same four body plans be selected? He thought it unlikely.

Obviously, we can't repeat the Burgess Shale, but Ken Olsen, an associate professor of biology at Washington University in St. Louis, says there are other ways to ask whether evolution is repeatable. One is to look at related species that have independently evolved the same traits and ask if the same genes are responsible and, if so, whether the same mutations led to the trait.


A research group uncovered that the development of wings in fruit flies does not progress synchronously with the organism's development. Instead, it is coordinated with the whole body only at distinct 'milestones'. This study helps explain how an organism facing environmental and physiological perturbations retains the ability to build correct functional organs and tissues in a proportional adult body.


During evolutionary diversification of vertebrate limbs, the number of toes in even-toed ungulates such as cattle and pigs was reduced and transformed into paired hooves. Scientists at the University of Basel have identified a gene regulatory switch that was key to evolutionary adaption of limbs in ungulates. 


Fossilized fish specimens from the Canadian Rockies, known as Metaspriggina,
dates from the Cambrian period (around 505 million years ago), shows pairs of exceptionally well-preserved arches near the front of its body. The first of these pairs, closest to the head, eventually led to the evolution of jaws in vertebrates, the first time this feature has been seen so early in the fossil record.  


On the island of Java, in Indonesia, the silvery gibbon, an endangered primate, lives in the rainforests and engages in behavior that's unusual for a primate - it sings long, complicated songs, using 14 different note types, that signal territory and send messages to potential mates and family.

Far from being a mere curiosity, the silvery gibbon may hold clues to the development of language in humans, according to a paper which asserts that by re-examining contemporary human language, we can see indications of how human communication could have evolved from the systems underlying the older communication modes of birds and other primates.


For the last 2.5 million years, our planet has experienced lengthy cold cycles with brief interruptions by warm ones. During cold periods, continental-scale ice sheets blanketed large tracts of the northern hemisphere and as the climate warmed up, these colossal glaciers receded, leaving Yosemite-like valleys and other majestic geologic features behind.

Obviously, the advance and retreat of the ice sheets also had a profound influence on the evolution and geographic distribution of many animals, including those that live today in the Arctic regions.