Navigation Links
East-African human ancestors lived in hot environments, says Caltech-led team
Date:6/8/2010

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
lorio@caltech.edu
626-395-3631
California Institute of Technology
Source:Eurekalert

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:
*Name:
*Comment:
*Email:
(Date:2/2/2016)... Feb. 2, 2016 This BCC Research ... market by reviewing the recent advances in high ... drive the field forward. Includes forecast through 2019. ... the challenges and opportunities that exist in the ... solution developers, as well as IT and bioinformatics ...
(Date:2/2/2016)...   Parabon NanoLabs (Parabon) announced today ... Office and the Defense Forensics and Biometrics Agency ... company,s Snapshot Kinship Inference software for ... defense-related DNA forensics.  Although Snapshot is best known ... ancestry from DNA evidence), it also has the ...
(Date:2/1/2016)... 2016  Today, the first day of American Heart ... develop a first of its kind workplace health solution ... In the first application of Watson ... ), and Welltok will create a new offering that ... analytics, delivered on Welltok,s health optimization platform. The effort ...
Breaking Biology News(10 mins):
(Date:2/11/2016)...   BioInformant announces the February 2016 release ... Opportunities, Tools, and Technologies – Market Size, Segments, Trends, ... The first and only market ... BioInformant has more than a decade of historical information ... stem cell type. This powerful 175 page global strategic ...
(Date:2/11/2016)... Miami (PRWEB) , ... February 11, 2016 , ... ... opening of its new stem cell treatment clinic in Quito, Ecuador. The new ... orthopedic and trauma applications to patients from around the world. , The ...
(Date:2/10/2016)... ANNAPOLIS, Md. , Feb. 10, 2016  The ... E. Busch , has announced that University of Maryland ... MD, PhD, MBA and University of Maryland Medical System ... recipients of the "Speaker,s Medallion," the highest honor given ... House of Delegates. Dean Reece and ...
(Date:2/10/2016)... ... February 10, 2016 , ... ... that it has joined the Human Vaccines Project, a public-private partnership to ... cancer. , The Human Vaccines Project brings together leading pharmaceutical and ...
Breaking Biology Technology: