Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. Earth Science News .




ABOUT US
Fluctuating environment may have driven human evolution
by Staff Writers
University Park PA (SPX) Dec 27, 2012


The researchers examined lake sediments from Olduvai Gorge in northern Tanzania, looking for biomarkers - fossil molecules - from ancient trees and grasses. Credit: Credit: Gail Ashley.

A series of rapid environmental changes in East Africa roughly 2 million years ago may be responsible for driving human evolution, according to researchers at Penn State and Rutgers University. "The landscape early humans were inhabiting transitioned rapidly back and forth between a closed woodland and an open grassland about five to six times during a period of 200,000 years," said Clayton Magill, graduate student in geosciences at Penn State.

"These changes happened very abruptly, with each transition occurring over hundreds to just a few thousand years." According to Katherine Freeman, professor of geosciences, Penn State, the current leading hypothesis suggests that evolutionary changes among humans during the period the team investigated were related to a long, steady environmental change or even one big change in climate.

"There is a view this time in Africa was the 'Great Drying,' when the environment slowly dried out over 3 million years," she said. "But our data show that it was not a grand progression towards dry; the environment was highly variable."

According to Magill, many anthropologists believe that variability of experience can trigger cognitive development.

"Early humans went from having trees available to having only grasses available in just 10 to 100 generations, and their diets would have had to change in response," he said.

"Changes in food availability, food type, or the way you get food can trigger evolutionary mechanisms to deal with those changes. The result can be increased brain size and cognition, changes in locomotion and even social changes - how you interact with others in a group. Our data are consistent with these hypotheses.

"We show that the environment changed dramatically over a short time, and this variability coincides with an important period in our human evolution when the genus Homo was first established and when there was first evidence of tool use."

The researchers - including Gail Ashley, professor of earth and planetary sciences, Rutgers University - examined lake sediments from Olduvai Gorge in northern Tanzania.

They removed the organic matter that had either washed or was blown into the lake from the surrounding vegetation, microbes and other organisms 2 million years ago from the sediments. In particular, they looked at biomarkers - fossil molecules from ancient organisms - from the waxy coating on plant leaves.

"We looked at leaf waxes because they're tough, they survive well in the sediment," said Freeman.

The team used gas chromatography and mass spectrometry to determine the relative abundances of different leaf waxes and the abundance of carbon isotopes for different leaf waxes. The data enabled them to reconstruct the types of vegetation present in the Olduvai Gorge area at very specific time intervals.

The results showed that the environment transitioned rapidly back and forth between a closed woodland and an open grassland.

To find out what caused this rapid transitioning, the researchers used statistical and mathematical models to correlate the changes they saw in the environment with other things that may have been happening at the time, including changes in the Earth's movement and changes in sea-surface temperatures.

"The orbit of the Earth around the sun slowly changes with time," said Freeman. "These changes were tied to the local climate at Olduvai Gorge through changes in the monsoon system in Africa.

Slight changes in the amount of sunshine changed the intensity of atmospheric circulation and the supply of water. The rain patterns that drive the plant patterns follow this monsoon circulation. We found a correlation between changes in the environment and planetary movement."

The team also found a correlation between changes in the environment and sea-surface temperature in the tropics.

"We find complementary forcing mechanisms: one is the way Earth orbits, and the other is variation in ocean temperatures surrounding Africa," Freeman said.

The researchers recently published their results in the Proceedings of the National Academy of Sciences along with another paper in the same issue that builds on these findings. The second paper shows that rainfall was greater when there were trees around and less when there was a grassland.

"The research points to the importance of water in an arid landscape like Africa," said Magill. "The plants are so intimately tied to the water that if you have water shortages, they usually lead to food insecurity.

"Together, these two papers shine light on human evolution because we now have an adaptive perspective. We understand, at least to a first approximation, what kinds of conditions were prevalent in that area and we show that changes in food and water were linked to major evolutionary changes."

.


Related Links
Penn State
All About Human Beings and How We Got To Be Here






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





ABOUT US
Study: Human hands evolved as weapons
Salt Lake City (UPI) Dec 19, 2012
Hands evolved not only for manual dexterity needed to use tools or create art but also so people could make fists and fight, University of Utah researchers say. Humans have shorter palms and fingers than apes and longer, stronger, more flexible thumbs - features long thought to have evolved to give humans the manual dexterity to make and use tools - but "the proportions of our hands a ... read more


ABOUT US
Burst shark aquarium hurts 15 in Shanghai shopping centre

26 injured in Macau-Hong Kong ferry collision

US Navy sailors sue Japan's TEPCO over radiation

Fukushima operator boosts compensation estimate

ABOUT US
Malaysia convoy in Australia rare earth plant protest

All Systems Go for Highest Altitude Supercomputer

Foam's Future Seen in Space and Industry

General Dynamics Delivers Digital Video Exploitation System to Australian Army for Operations in Afghanistan

ABOUT US
Hope for polluted lagoon near Rio Olympic village?

Smaller Colorado River projected for coming decades

China's boom savages coral reefs: study

Spanish consumers prefer national fish

ABOUT US
CryoSat hits land

Study shows rapid warming on the West Antarctic Ice Sheet

Antarctic science drill project called off

W. Antarctic warming among world's fastest

ABOUT US
Even in same vineyard, different microbes may create variations in wine grapes

What's in a name? Everything for Farmers

Bumblebees do best where there is less pavement and more floral diversity

Why some grasses evolved a more efficient photosynthesis and others didn't

ABOUT US
5.5-magnitude quake strikes off Japan: USGS

Thousands flee floods as cyclone batters Solomon Islands

Fresh cyclone brews in Pacific

Two dead as Malaysian floods subside

ABOUT US
China firm to acquire major African iron ore mine: Xinhua

Canada mulls joining Mali training effort

C.Africa army routed trying to recapture rebel-held city

Ghana bans import of second-hand fridges

ABOUT US
Fluctuating environment may have driven human evolution

Decision to give a group effort in the brain

Scientists construct first map of how the brain organizes everything we see

Do palm trees hold the key to immortality?




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement