Navigation Links
East-African human ancestors lived in hot environments, says Caltech-led team

PASADENA, Calif.East Africa's Turkana Basin has been a hot savanna region for at least the past 4 million yearsincluding the period of time during which early hominids evolved in this areasays a team of researchers led by scientists at the California Institute of Technology (Caltech). These findings may shed light on the evolutionary pressures that led humans to walk upright, lose most of our body hair, develop a more slender physique, and sweat more copiously than other animals.

Their findingswhich were based on measurements of the spatial distribution and concentrations of isotopes in carbonate ionsare being reported this week in the early online edition of the Proceedings of the National Academy of Sciences (PNAS).

"When you measure the temperature of the ground, you learn a lot about the environment above it," says John Eiler, Robert P. Sharp Professor of Geology and professor of geochemistry at Caltech. In fact, he says, soil temperature tells you not just about air temperature, but about whether there were trees and plants to shade the soil, keeping temperatures cooler during the hottest part of the day.

Today, northern Kenyawhere the Turkana Basin is foundis among the warmest areas on earth. It has little canopy forest, leaving the ground exposed to sunlight. "The question is, was the ground here ever cooler than it is today?" asks Eiler. "And if it was, why? Was it because the air was cooler, or because of more forest shading?"

To find out, the team examined the spatial organization (or "clumping") of rare, naturally occurring isotopes of carbon and oxygenspecifically, carbon-13 and oxygen-18in the form of carbonate ions that are constituents of minerals found in buried soils from northern Kenya. The clumping of these isotopes, Eiler and his colleagues have demonstrated in previous papers, is dependent on temperature: Hot temperatures lead to less clumping; cold temperatures, more.

"These carbonates are a common constituent of these soils," Eiler explains. "If you have the ability to measure their isotopes, then you have a ground-temperature thermometer."

When the researchers applied that thermometer to various layers of buried soils from East Africa, they found what Eiler says was "such a straightforward answer, it wasn't obvious how we could talk ourselves out of the conclusion we reached."

That conclusion? "The Turkana Basin regionone of the key places where hominid fossils documenting human evolution are foundhas been a really hot place for a really long time," says Benjamin Passey, formerly a postdoctoral scholar at Caltech. Passey, who led the work on this project, is now at Johns Hopkins University.

But why does it matter how hot Africa was millions of years ago? "This is the area where we find the occurrence of some of the earliest hominid species," notes Eiler. "It tells us that this environment, though harsh, was a place where our ancestors could thrive. It tells us that they were probably originally marginal species that lived in difficult-to-survive environments."

The findings also shed some lightand heaton a longstanding debate over the origin of bipedalism in early humans.

"For a long time, anthropologists have hypothesized that bipedalism and other unique human traits would be advantageous to life in hot savanna environments," says Passey. "For example, by standing upright, we intercept less direct sunlight than if we were on all fours, and in hot, open environments, the ground and near-surface air can be appreciably hotter than the air a few feet above the ground. So, by standing upright, we are avoiding a high-temperature environment."

Of course, Passey adds, this strategy would only be of significant use if the environment in question is indeed a high-temperature one. "In cooler environments, these traits do not really have a thermal advantage," he notes. These considerations led to the team's interest in figuring out just how hot it was in the part of the world where bipedalism is most likely to have first gained a toehold.

Eiler cautions that the team's findings are simply assessments of the area's temperature over time, and have nothing to say about "the importance of ambient temperature in shaping human evolution." But, he notes, they are "consistent with the notion that the heat in the area would have been a selective pressure that could have made bipedalism advantageous."


Contact: Lori Oliwenstein
California Institute of Technology

Related biology news :

1. Gene regulation, not just genes, is what sets humans apart
2. Antioxidant overload may underlie a heritable human disease
3. Facial attraction -- choice of sexual partner shaped the human face
4. Humans fostering forest-destroying disease
5. SRMs track fire retardants in humans and environment
6. St. Jude influenza survey uncovers key differences between bird flu and human flu
7. Human derived stem cells can repair rat hearts damaged by heart attack
8. Influence of sex and handedness on brain is similar in capuchin monkeys and humans
9. Gene regulation in humans is closer than expected to simple organisms
10. Pittsburgh scientists identify human source of stem cells with potential to repair muscle
11. Researchers developing device to predict proper light exposure for human health
Post Your Comments:
(Date:11/9/2015)... ) ... "Global Law Enforcement Biometrics Market 2015-2019" ... ) has announced the addition of ... 2015-2019" report to their offering. ... ) has announced the addition of the ...
(Date:10/29/2015)... LA JOLLA, Calif. , Oct. 29, 2015 /PRNewswire-USNewswire/ ... released a new report titled, "DNA Synthesis and Biosecurity: ... how well the Department of Health and Human Services ... was issued in 2010. --> ... advances, but it also has the potential to pose ...
(Date:10/29/2015)... NEW YORK , Oct. 29, 2015 /PRNewswire/ ... wearable technology, announced a partnership with 2XU, a ... accessories, to deliver a smart hat with advanced ... runners and other athletes to monitor key biometrics ... of the strategic partnership, the two companies will bring ...
Breaking Biology News(10 mins):
(Date:11/24/2015)... CITY , Nov. 24, 2015 /PRNewswire/ - ... "Company") announced today that the remaining 11,000 post-share ... Share Purchase Warrants (the "Series B Warrants") subject ... were exercised on November 23, 2015, which will ... Shares.  After giving effect to the issuance of ...
(Date:11/24/2015)... , Nov. 24, 2015 /CNW Telbec/ - ProMetic Life Sciences ... today that Mr. Pierre Laurin , President and Chief ... at the upcoming Piper Jaffray 27 th Annual Healthcare ... on December 1-2, 2015. st , at ... one-on-one meetings throughout the day. The presentation will be available ...
(Date:11/24/2015)... ... November 24, 2015 , ... Whitehouse Laboratories is pleased to announce that ... facility will be strictly dedicated to basic USP 61, USP 62 and USP 51 ... to have complete chemistry and micro testing performed by one supplier. Management ...
(Date:11/23/2015)... ... November 23, 2015 , ... Shimadzu Corporation announces ... Nexera UC Unified Chromatography system. The award from R&D magazine recognizes Shimadzu’s Nexera ... the year in the analytical and testing category. R&D Magazine chose the Nexera ...
Breaking Biology Technology: