Genomics on EARTH Magazine

Denisovan DNA found in modern Pacific Islanders, ancient Spaniards

Thu, 14 Jul 2016 10:21:16 -0400

Denisovans were first identified from a 41,000-year-old finger bone found in a cave in Siberia. In two new studies, traces of Denisovan DNA have been found in modern Melanesians and in 430,000-year-old remains at the Sima de los Huesos site in Spain. Credit: K. Cantner, AGI.

In the time that Homo sapiens and Neanderthals were coexisting — and interbreeding — there was at least one more human species on the landscape, the Denisovans. First identified from a 41,000-year-old finger bone found in a cave in Siberia, the Denisovans are now thought to have been widespread around Eurasia. In two new studies, scientists have shed additional light on the relationship of Denisovans to other humans, finding new traces of Denisovan DNA in ancient and modern genomes.

A long layover on the Bering land bridge

Wed, 16 Mar 2016 20:22:15 -0400

The Late Pleistocene remains of two infants recovered from the Upper Sun River campsite in eastern Alaska are shedding light on the peopling of the Americas. Credit: K. Cantner, AGI, after Tackney, et al. 2015.

About 11,500 years ago, two infants were laid to rest side by side in a shallow grave 80 kilometers southeast of what is now Fairbanks, Alaska. The area was once part of Beringia, a strip of ice-free land connected to Asia during the last ice age. Researchers found the remains in 2013, and have now sequenced the complete mitochondrial genomes of the two children. The results revealed that the infants had different mothers and that their genetic signatures are found today throughout North and South America.

Land plants came prepared for terrestrial life

Thu, 07 Jan 2016 10:54:54 -0500

Nitella hyalina is a stonewort and a member of the charophyte green algae family. No known charophyte alga has symbiotic associations with mycorrhizal fungi, but N. hyalina and other stoneworts do develop root-like rhizoids that anchor the thallus in sand and mud, and probably frequently interact with fungi. The frame is about 5 millimeters tall. Credit: Charles F. Delwiche, University of Maryland, all rights reserved.

Plants colonized land between 450 million and 420 million years ago, and, once there, they drastically altered terrestrial landscapes and provided resources for animals leaving the oceans around the same time. One adaptation that helped plants gain a foothold on land is a symbiosis with fungi known as arbuscular mycorrhizae (AM), which help plants acquire water and key nutrients from the soil and are still associated with most land plants today. In return, plants provide the fungi with bioavailable carbon produced during photosynthesis. When this symbiosis evolved has remained unclear, but researchers recently discovered that it likely has roots in a group of freshwater algae ancestral to land plants.

Benchmarks: July 11, 1997: Neanderthal DNA unraveled

Tue, 27 Oct 2015 12:39:33 -0400

Artist's rendering of Neanderthals. Credit: art by Randii Oliver.

On July 11, 1997, six scientists announced they had sequenced DNA from a Neanderthal fossil. It was the first time anyone had analyzed the genetics of an extinct hominin, and the findings gave paleoanthropologists a new perspective on Neanderthals’ place in the human family tree.

Tree of life reshaped

Thu, 08 Oct 2015 10:38:03 -0400

Researchers considered several possible scenarios depicting the relationship between eukaryotes and two groups of archaea: the TACK group and Euryarchaeota. Three variations of scenario 1 all indicate a common, but unknown, root for all three groups, with eukaryotes being a sister lineage to either or both the TACK archaea and Euryarchaeota. Scenario 2 depicts the TACK group as the root of Archaea, with the eukaryotes and Euryarchaeota as sisters. Scenario 3 — the most likely according to the new study — depicts Euryarchaeota as the root of Archaea, with the eukaryotes and the TACK archaea as sisters. Credit: K. Cantner, AGI, after Raymann et al., PNAS, 2015.

Since the 1970s, the classic “tree of life” taught in classrooms has portrayed three domains of life — Archaea, Bacteria and Eukaryota — all descending from an unknown common ancestor. But behind the scenes, this textbook picture has been shifting. Many scientists now think the tree’s deepest root lies within the bacteria; and, even more recently, some have begun suspecting that the Eukaryota — including all animals, plants, fungi, slime molds and other organisms whose cells have nuclei — are actually an offshoot from the Archaea, paring the tree from three to two domains. Now, a new study furthers that claim, and with the help of a novel technique for parsing phylogenetic data in greater detail than ever before, suggests a revised backstory for the Archaea — and, by extension, us.

Kennewick Man related to modern Native Americans

Mon, 21 Sep 2015 11:41:42 -0400

Cast and facial reconstruction of Kennewick Man. Previous morphometric analyses suggested he was related to the Ainu people of Japan, but a new genomic analysis shows he is more closely related to modern Native Americans. Credit: Chip Clark, Smithsonian.

After two decades of controversy surrounding the origins of Kennewick Man — a 9,000-year-old skeleton found on the banks of the Columbia River in Washington state — a genomic analysis has revealed that he was, in fact, related to modern Native Americans. The 1996 discovery of the well-preserved skeleton led to a protracted legal battle among scientists, Native American tribes and the federal government over the disposition of the remains, and sparked a scientific debate about the origins of the first Americans.

Snake forebear had two back legs but no front legs

Fri, 21 Aug 2015 12:32:06 -0400

This artist's rendering of the common ancestor of modern snakes shows it with two small hind legs. Credit: Julius T. Csotonyi.

The more than 3,400 species of snakes alive today may have descended from one ancestor that lacked forelimbs, but which had small vestigial hind limbs complete with ankle bones and toes, according to a new study published in BMC Evolutionary Biology.

Bird genomes untangle branches of avian family tree

Tue, 07 Apr 2015 13:24:30 -0400

Birds are one of the most diverse groups of vertebrates on Earth, with more than 10,000 known species. Credit: ©Shutterstock.com/Tom Reichner.

Birds, the only surviving descendants of dinosaurs, have one of the most fascinating — and perplexing — family trees in the animal kingdom. To sort it out, an international collaboration known as the Avian Phylogenomics Project has sequenced the genomes of dozens of different bird species, representing all the orders in the bird family. Even with a glut of new data, however, many questions remain about the branches of the avian family tree.