Jan 25, 2018

Axios Science

By Alison Snyder
Alison Snyder

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Human fossils found in Israel are oldest to date

The upper left jaw of an ancient human fossil found in Israel. Photo: Israel Hershkovitz / Tel Aviv University

Axios' Erin Ross writes: A ridge of teeth discovered in a cave in Israel are between 177,000-194,000 years old, according to a paper published today in Science.

The teeth appear to be human, and if they are, would be the oldest anatomically modern human fossil found outside of Africa and the oldest fossil with modern human traits found to date.

What it means: Fossils like these, and new gene sequencing tools, are starting to answer questions about when modern humans left Africa, and when, exactly, they became human. The find in Israel suggests modern humans may have left Africa earlier than previously thought.

What they found: Debbie Guatelli-Steinberg, a paleoanthropologist at Ohio State University who was not involved in the study, tells Axios that the specimen's teeth and jaw structure are most like humans, and don't have Neanderthal features.

And, they didn’t just find a jaw — they unearthed sophisticated stone tools, too.

Dig deeper: Read Erin's full story here.

Axios stories for your brain
Coral reefs endangered by massive plastic pollution

Plastic pollution, such as this Nike logo, helps foster certain diseases like white syndrome coral disease seen here. Photo: Joleah Lamb / Cornell University

The billions of pieces of plastic waste hovering in the oceans of the Asia-Pacific region are causing a 20-fold increased risk of diseases deadly to coral reefs, according to a new study published in Science Thursday, Axios' Eileen Drage O'Reilly reports.

Why it matters: The estimated 11.1 billion plastic items lodged around the Asia-Pacific coral reefs boost the risk of coral contracting skeletal eroding band disease, white syndromes, and black band disease, they found. About 275 million people in the region rely on the reefs for food, tourism, marine biodiversity, and coastal protection.

"Plastic is a triple whammy for coral infections — it abrades and cuts open the skin of the coral, and then can convey pathogenic microorganisms. [It] shades and cuts off water flow," study author C. Drew Harvell tells Axios.

Dive deeper: Read the rest of Eileen's story here.

What we're reading elsewhere
Something wondrous

The Mexican axolotl Ambystoma mexicanum is a model organism for regeneration research. Photo: IMP Vienna

The critically endangered Mexican axolotl can regenerate body parts better than practically any other vertebrate on the planet. If a limb is lost, a limb can be regrown.

"We need to figure out why and hopefully mimic that in humans," says Northeastern University's James Monaghan, who studies the biology of regeneration in the salamander species. The programs of development that give us our forms in the womb shut down in humans as we grow — but axolotls and some other animals keep that ability forever.

For a long time, researchers have tried to sequence the animal's genome in order to better understand how cells can know what was lost and what to regenerate. But the tiny salamander has a big genome — at 32 billion base pairs, it's ten times the size of the human genome — filled with lots of repetitive sequences that make it hard to sequence. It is like putting together a puzzle that has a lot of the same pieces, says Monaghan.

What's new: Scientists figured out a way to piece together the axolotl genome and this week reported a nearly complete sequence.

  • The salamander's genome may be 10 times larger than that of humans but it has only slightly more genes (about 23,000).
  • They found 3 genes that birds, mammals and reptiles don't have and that accumulate in the cells of regenerating limbs, though their role is unknown.
  • Between the genes that encode proteins are long stretches of DNA. (Most species have them, including us but in not nearly the same abundance as axolotls.) In earlier work, researchers found some of these DNA elements are activated during regeneration.
  • "Now we can say this particular gene turns on only during regeneration and what drives it," Monaghan says about the new genome sequence, work he was not involved in. "It gives us access to the regulatory elements, which are key pieces of the puzzle to understanding regeneration."
  • It goes beyond limbs. The salamander species can also regenerate their ovaries, lungs, brain, heart, spinal cord and parts of their retina. Little is known about how their internal organs can regrow. The next step is to figure out whether they use the same pathways, Monaghan says.

One more thing: The researchers found the axolotl's developmentally important genes aren't as big as their other genes. "There has been selection to keep them small," says Monaghan. It is speculation at this point but it could be so they can be transcribed quickly when needed — say, during regeneration.

Alison Snyder

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