Navigation Links
Giants among us: Paper explores evolution of the world’s largest mammals

Athens, Ga. The largest mammal that ever walked the earthIndricotherium transouralicum, a hornless rhinoceros-like herbivore that weighed approximately seventeen tons and stood about eighteen feet high at the shoulderlived in Eurasia almost 34

Athens, Ga. The largest mammal that ever walked the earthIndricotherium transouralicum, a hornless rhinoceros-like herbivore that weighed approximately seventeen tons and stood about eighteen feet high at the shoulderlived in Eurasia almost 34 million years ago. In a paper just published in the journal Science, an international team of researchers has compiled and analyzed an enormous database of information about the largest mammals across time and around the globe, revealing striking patterns in their evolution.

The research, funded by a National Science Foundation Research Coordination Network grant, was led by scientists at the University of New Mexico, who brought together paleontologists, evolutionary biologists and macroecologists from universities around the world. University of Georgia Odum School of Ecology dean John Gittleman and postdoctoral researcher Patrick Stephens were among them.

"We were invited to participate because the group wanted to take an explicitly evolutionary approach to size," said Gittleman, whose research focuses on large-scale ecological and evolutionary problems, from disease to extinction to organism characteristics.

"John and Patrick were indispensable members of our team," said Felisa Smith, associate professor of biology at the University of New Mexico and the paper's lead author. "This really was a project that took all of us to accomplish."

The goal of the research was to revisit key questions about size, specifically in mammals. "Size impacts everything, from reproduction to extinction," said Gittleman. "And mammals are a good test case. There is so much variationeverything from mice to elephantsand there is also far more data available about mammals than other taxonomic groups."

"There is a much better fossil record for mammals than for many other groups," Stephens said. "That's partly because mammals' teeth preserve really well. And as it happens, tooth size correlates well with overall body size."

The researchers spent two years assembling the data. "The database is powerful and unique," said Gittleman. "It includes information on the size of all mammals, living and fossil, from around the world."

With access to so much information, the group was able to test a hypothesis about the evolution of mammal size.

"During the Mesozoic, mammals were small," said Gittleman. "Once dinosaurs went extinct, mammals evolved to be much larger as they diversified to fill ecological niches that became available. This phenomenon has been well-documented for North America; we wanted to know if the same thing happened all over the world."

The researchers found that the pattern was indeed consistent, not only globally but across time and across trophic groups and lineagesthat is, animals with differing diets and descended from different ancestorsas well. The maximum size of mammals began to increase sharply about 65 million years ago, peaking in the Oligocene Epoch (about 34 million years ago) in Eurasia, and again in the Miocene Epoch (about 10 million years ago) in Eurasia and Africa.

"Having so many different lineages independently evolve to such similar maximum sizes suggests that there were similar ecological roles to be filled by giant mammals across the globe," said Gittleman. "The consistency of the pattern strongly implies that biota in all regions were responding to the same ecological constraints."

Global temperature and the amount of land available as an animal's range are two ecological factors that appear to correlate with the evolution of maximum body size, but Gittleman warned against assigning cause and effect. "A big part of science is seeing patterns, and then producing new hypotheses and testing them," he said. "We have now identified this pattern very rigorously."


Contact: John Gittleman
University of Georgia

Related biology news :

1. Canopy giants and miniature fungi among 250 new species discovered in Kews 250th anniversary year
2. Overweight primarily a problem among wealthier women in low- to middle-income countries
3. Social support post-cancer lacking among minority women
4. Father absence linked to earlier puberty among certain girls
5. Immune responses during pregnancy linked to schizophrenia among offspring
6. The fungus among us: A new way of decomposing BPA-containing plastic
7. Scientific expertise lacking among doubters of climate change, says Stanford-led analysis
8. Fungus among us could become non-food source for biodiesel production
9. UM School of Medicine study finds vaginal microbes vary among healthy women
10. LSU identifies community conditions related to malnutrition deaths among older adults
11. Home medication errors common among children with chronic conditions
Post Your Comments:
(Date:4/26/2016)... , April 27, 2016 ... the  "Global Multi-modal Biometrics Market 2016-2020"  report to ... ) , The analysts forecast the ... CAGR of 15.49% during the period 2016-2020.  ... number of sectors such as the healthcare, BFSI, ...
(Date:4/14/2016)... TEL AVIV, Israel , April 14, 2016 /PRNewswire/ ... in Behavioral Authentication and Malware Detection, today announced the ... has already assumed the new role. Goldwerger,s ... for BioCatch, on the heels of the deployment of ... In addition, BioCatch,s behavioral biometric technology, which discerns unique ...
(Date:3/29/2016)... Florida , March 29, 2016 ... the "Company") LegacyXChange "LEGX" and SelectaDNA/CSI Protect are pleased ... in ink used in a variety of writing instruments, ... Buyers of originally created collectibles from athletes on LegacyXChange ... forensic analysis of the DNA. Bill ...
Breaking Biology News(10 mins):
(Date:6/27/2016)... Ginkgo Bioworks , a leading organism design company ... as one of the World Economic Forum,s Technology ... companies. Ginkgo Bioworks is engineering biology to manufacture ... the nutrition, health and consumer goods sectors. The ... Fortune 500 companies to design microbes for their ...
(Date:6/24/2016)... Epic Sciences unveiled a liquid biopsy ... PARP inhibitors by targeting homologous recombination deficiency (HRD) ... test has already been incorporated into numerous clinical ... Over 230 clinical trials are investigating ... PARP, ATM, ATR, DNA-PK and WEE-1. Drugs targeting ...
(Date:6/24/2016)... , ... June 24, 2016 , ... Researchers at the ... commonly-identified miRNAs in people with peritoneal or pleural mesothelioma. Their findings are the subject ... it now. , Diagnostic biomarkers are signposts in the blood, lung fluid or ...
(Date:6/23/2016)... ... June 23, 2016 , ... UAS LifeSciences, one of ... their brand, UP4™ Probiotics, into Target stores nationwide. The company, which has been ... Target to its list of well-respected retailers. This list includes such fine stores ...
Breaking Biology Technology: