Navigation Links
Did humans cause ecosystem collapse in ancient Australia?

Massive extinctions of animals and the arrival of the first humans in ancient Australia may be linked, according to scientists at the Carnegie Institution, University of Colorado, Australian National University, and Bates College.* The extinctions occurred 45,000 to 55,000 years ago. The researchers traced evidence of diet and the environment contained in ancient eggshells and wombat teeth over the last 140,000 years to reconstruct what happened. The remains showed evidence of a rapid change of diet at the time of the extinctions. The researchers believe that massive fires set by the first humans may have altered the ecosystem of shrubs, trees, and grasses to the fire-adapted desert-scrub of today. The work is published in the July 8, issue of Science.

The scientists plotted diet changes over 140,000 years of two species of large, flightless birds--the now-extinct Genyornis and the surviving emu (Dromaius)--in three Australian locations. They then corroborated their findings by analyzing ancient wombat teeth. "What your mother told you is true: You are what you eat," stated co-author of the study Marilyn Fogel of Carnegie. "Eggshells and teeth both contain evidence of these animals' diets in different forms of carbon. All three animals were plant eaters. Different types of plants metabolize different forms of carbon in distinctive ways from the CO2 they take up during photosynthesis. The tell-tale carbon varieties were preserved in the eggshells and teeth and told us what types of plants the animals ate. We saw a sudden shift in plant type coincident with the arrival of humans. The shifting diet shed light on the extinctions. The animals that relied mostly on the more palatable plant forms died out, such as Genyornis, while the animals that adapted to the less nutritious plants survived, including the emu."

There are three isotopes, or varieties, of carbon found in nature--12C, 13C and 14C. They differ in the number of neutrons in the nucleus. By far the most abundant variety is in the lightest, 12C. About 1% is 13C, a heavier sibling with an additional neutron. There is even less 14C, the unstable, radioactive heavyweight of them all.

"13C is the key," Fogel explained. "There are two main ways plants metabolize 13C . About 85% of plants belong to what is known as C3 photosynthesis group. This group incorporates less 13C than plants belonging to the second most common class, C4. Thus, the differences in 13C that we detected in the eggshells and teeth pointed to the type of plants that were consumed. Although, both types of plants were present before the extinctions, we saw a quick shift in dominance from C4 drought-resistant trees, shrubs and grasses, to C3 desert plants. "

Why did the scientists point to humans as the instigators of the ecological changes? First, they ruled out the other usual suspect--global climate change. They looked at their data in 15,000-year intervals back to 140,000 years ago. The period included dramatic climate changes, but no changes in the diet and environment until an abrupt transition was noted that corresponded to the arrival of humans. "Humans are the major suspect," commented Fogel. "However, we don't think that over-hunting or new diseases are to blame for the extinctions, because our research sees the ecological transition at the base of the food chain. Bands of people set large-scale fires for a variety of reasons, including hunting, clearing, and signaling other bands. Based on the evidence, human-induced change in the vegetation is the best fit to explain what happened at that critical juncture."


'"/>

Source:Carnegie Institution


Related biology news :

1. Yale researchers identify molecule for detecting parasitic infection in humans
2. Friendly bacteria in humans may protect against HIV
3. The lopsided brain: Attention bias is shared by humans and birds
4. Oldest cranial, dental and postcranial fossils of early modern European humans confirmed
5. Retrovirus struck ancestors of chimpanzees and gorillas millions of years ago, but did not affect ancestral humans
6. UI researcher studies deafness in fruit flies, humans
7. Chickadees can help humans get their bearings
8. Study shows humans have ability to track odors, much like bloodhounds
9. Caloric restriction wont dramatically extend life span in humans: UCLA research
10. Study identifies gene in mice that may control risk-taking behavior in humans
11. Primate virus jumps species barrier to humans for first time in Asia
Post Your Comments:
*Name:
*Comment:
*Email:


(Date:6/20/2016)... June 20, 2016 Securus Technologies, a ... solutions for public safety, investigation, corrections and monitoring ... involved, it has secured the final acceptance by ... for Managed Access Systems (MAS) installed. Furthermore, Securus ... to be installed by October, 2016. MAS distinguishes ...
(Date:6/7/2016)... June 7, 2016  Syngrafii Inc. and San ... relationship that includes integrating Syngrafii,s patented LongPen™ eSignature ... This collaboration will result in greater convenience for ... union, while maintaining existing document workflow and compliance ... ...
(Date:6/1/2016)... , June 1, 2016 Favorable ... Election Administration and Criminal Identification to Boost Global Biometrics ... recently released TechSci Research report, " Global Biometrics Market ... Competition Forecast and Opportunities, 2011 - 2021", the global ... by 2021, on account of growing security concerns across ...
Breaking Biology News(10 mins):
(Date:6/23/2016)... Wausau, WI (PRWEB) , ... June 23, 2016 ... ... probiotic supplements, is pleased to announce the launch of their brand, UP4™ Probiotics, ... supplements for over 35 years, is proud to add Target to its list ...
(Date:6/23/2016)... Lawrence, MA (PRWEB) , ... June 23, 2016 ... ... the Peel Plate® YM (Yeast and Mold) microbial test has received AOAC Research ... test platform of microbial tests introduced last year,” stated Bob Salter, Vice President ...
(Date:6/23/2016)... ... ... STACS DNA Inc., the sample tracking software company, today announced that Dr. ... STACS DNA as a Field Application Specialist. , “I am thrilled that Dr. ... STACS DNA. “In further expanding our capacity as a scientific integrator, Hays brings a ...
(Date:6/23/2016)... , June 23, 2016 On Wednesday, ... at 4,833.32, down 0.22%; the Dow Jones Industrial Average edged ... closed at 2,085.45, down 0.17%. Stock-Callers.com has initiated coverage on ... ), Nektar Therapeutics (NASDAQ: NKTR ), Aralez Pharmaceuticals ... (NASDAQ: BIND ). Learn more about these stocks ...
Breaking Biology Technology: