Navigation Links
Birth rate, competition are major players in hominid extinctions

Modern human mothers are probably happy that they typically have one, maybe two babies at a time, but for early hominids, low birth numbers combined with competition often spelled extinction.

"The lineages of primates have some traits that make it hard for them to respond to rapid perturbations in the environment," says Dr. Nina G. Jablonski, professor of anthropology and department head at Penn State. "Through time we see a lot of lineages become extinct when environments where the species are found become highly seasonal or unpredictable."

Primates evolved in the Paleocene and Eocene when worldwide climate was less seasonal. The beneficial environment allowed primates to evolve as relatively brainy animals that reproduce slowly. However, when climate changed so that tropical forests shrunk and the environment became patchy, many species including primate species became extinct.

"While past primate populations moved with the forest, early hominid cultures 2.5 million years ago show signs of the ability to live in marginal areas and live on more dynamic, seasonal landscapes," Jablonski told attendees today (Feb. 16) at the annual meeting of the American Association for the Advancement of Science in San Francisco.

Through time, the human lineage evolved to fill a wide variety of ecological niches, but those species that filled narrow environments, were less able to withstand the effects of climate change. Paranthropus boisei, a Pleistocene hominid, thrived around 2.5 million years ago, but disappears from the fossil record a million years ago. Paranthropus boisei became extinct when it was unable to compete with other mammals.

A specialized feeder, Paranthropus boisei dined on hard objects like seeds, tubers and bones. While it had a variety of food sources, they all required the crunching, grinding force of its teeth. Unfortunately, bush pigs and hyenas had great grinding and crushing teeth, too, and went after the same food. Paranthropus could not compete because it produced one offspring a year at most, while the others had large litters and could increase their populations at a much faster rate. Paranthropus simply could not compete reproductively and could not alter its choice of food.

"We find that the early members of the genus Homo who succeeded were super ecological opportunists," says Jablonski. "They would eat vegetation and scavenge, kill small animals and forage."

Cultural adaptations helped these opportunists to take advantage of whatever food was available. But culture did not seem to help the Neandertal. Tremendously successful from about 200 to 50 thousand years ago, they suffered a gradual decrease and extinction from about 30 to 26 thousand years ago.

"Neandertal was extremely adept culturally," says Jablonski. "They had big brains, a wide variety of tools and were extremely successful as active, aggressive hunters of large game. We see evidence of hunting, kill sites, butchery and even herding off cliffs. We find thrusting spears and butchering knives." The Neandertal encountered increasing environmental seasonality with longer cold seasons and shorter periods of warm weather. Leading up to and during the last glacial maximum about 18,000 years ago, the grassy plains disappeared, taking with them the animals that relied on large expanses of grass for grazing. These animals were the prime food source for Neandertal.

At the same time, modern Homo sapiens experienced the same reduction in large animal game, but switched to also fishing, snaring small mammals like rabbits and capturing turtles and birds.

"Rather than being a specialized large mammal predator, modern humans would eat anything they could get their hands on. They eked out a living even if it meant eating grasshoppers or whatever," says Jablonski. "Even with this, modern humans barely hung on from 12 to 16,000 years ago.

"W hy did Neandertal not adapt culturally?" she asks. "Why did they not start eating bunnies? They did begin fishing."

Jablonski believes that competition from modern humans was already too strong. The environment was marginal and modern humans were already foraging and small-animal collecting.

"I think they were out-competed at the very end," says Jablonski. "Modern humans simply did it better, more nimbly."

She adds that modern humans may have had storage capabilities that Neandertal did not. There is evidence that modern humans did have the capacity to store food and water in the late Pleistocene. No evidence exists that Neandertal could store either.

Both Neandertal and modern humans suffered from the primate curses of single births widely spaced. For Neandertal, cultural adaptation was not sufficient to overcome and compete with modern humans, just as Paranthropus boisei could not compete with the likes of bush pigs and hyenas. " Can we, today, control our cultural behavior to ensure our environmental success," says Jablonski. "Can we control growth and population density, or come up with new technology to overcome the problems we will face from the global climate change we have created?

"We clearly have the cultural ability to do either," says the Penn State researcher. "But both require forethought and planning to face the demographic and climate change. A degree of honesty, our species is not known for."
'"/>

Source:Penn State


Related biology news :

1. Breast-Cancer Risk Linked to Exposure to Traffic Emissions at Menarche, First Birth
2. Birth defects: 8 million annually worldwide
3. Neandertal femur suggests competition with hyenas and a shift in landscape use
4. HIV exploits competition among T-cells
5. Columbia research lifts major hurdle to gene therapy for cancer
6. Researchers uncover sequence of major rice pathogen
7. Emergence of cancer as major cause of childhood death in developing countries is not being adequately addressed
8. Biochemists report discovery of structure of major piece of telomerase; implications for cancer
9. Virologists make major step towards understanding the process of HIV infection
10. Biota makes major antiviral discovery
11. New gene scanning technology marks a major advance in disease research

Post Your Comments:
*Name:
*Comment:
*Email:


(Date:3/15/2016)... 2016 Yissum Research Development Company of ... of the Hebrew University, announced today the formation of ... of various human biological indicators. Neteera Technologies has completed ... private investors. ... of electromagnetic emissions from sweat ducts, enables reliable and ...
(Date:3/10/2016)... March 10, 2016 --> ... research report "Identity and Access Management Market by Component ... and Governance), by Organization Size, by Deployment, by Vertical, ... by MarketsandMarkets, The market is estimated to grow from ... by 2020, at a Compound Annual Growth Rate (CAGR) ...
(Date:3/8/2016)...   Valencell , the leading innovator in ... secured $11M in Series D financing. The investment ... fund being launched by UAE-based financial services company ... TDF Ventures and WSJ Joshua Fund. Valencell plans ... growth and accelerate its pioneering innovation in accurate ...
Breaking Biology News(10 mins):
(Date:5/4/2016)... 4, 2016 According to a ... Market - Global Industry Analysis, Size, Share, Growth, Trends, ... anticipated to expand at a CAGR of 17.1% from ... 2024. Metabolomics is the extensive study of ... tissues or organisms. Together, these small molecules and their ...
(Date:5/4/2016)... New York, NY (PRWEB) , ... May 04, ... ... growth, has leveraged recent innovations in biotechnology to help treat hormonal and stress ... hair loss, Nutrafol® has captured the hearts of key opinion leaders in the ...
(Date:5/3/2016)... ... May 03, 2016 , ... Morf Media Inc ... training platform on mobile devices, today released a new interactive Food and ... Devices. The course is essential for owners or operators of places of business ...
(Date:5/3/2016)... Massachusetts (PRWEB) , ... May 03, 2016 , ... ... will gather at Boston CEO 2016 on May 31st and June 1st at ... networking forum for leading executives in the life sciences, offering exclusive access to ...
Breaking Biology Technology: