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  (Source: South Park Studios/Comedy Central)

Major evolutionary leaps occured at multiple points in the Earth's history (click to enlarge).  (Source: University of Bristol via Biology Letters)

Mammals did not take over until the dinosaurs died and they were presented with large amounts of free space, triggering evolution, according to the new theory. The theory indicates that space plays a more important role in evolution than competition.  (Source: SPL via BBC)
Senior colleague supports the Ph.D candidate's assertion that space proves a more critical factor than competition

There's a wealth of evidence that can be found in any university library -- biochemistry, fossils, and field biology -- supporting the theory that creatures have evolved to their current forms over the course of Terran life's existence over the last few billion years.  How they arrived there is still a topic of hot academic debate.

A controversial new study takes a crack at the topic of major evolutionary leaps.  While the concept of micro-evolution versus macro-evolution is considered outdated, there are times when creatures make bigger changes than others; take for the example the mammal's evolution from furry reptiles in the late Permian or early Triassic period.

While some, including the founder of modern evolutionary theory, Charles Darwin, theorized that competition was the driving factor in dramatic leaps, PhD student Sarda Sahney of the University of Bristol says living space is the primary driving force.

Ms. Sahney and her group's principle investigator, Professor Mike Benton, examined the fossil record and came to the conclusion that organisms made the biggest leaps when they were exposed to an uncolonized space -- somewhere 
devoid of competition.

Perhaps the evolutionary biologist's version of "nature abhors a vacuum", the hypothesis states that a creature -- say an ancient dinosaur -- gains a small evolution that allows it to access a vast uncolonized area -- for example flaps of skin under the arms that allow it to glide (briefly) into the air (an uncolonized arena), when jumping from trees.  

Pressure pushes the creature to accentuate that evolution with more changes (for example, bigger skin flaps to help it jump from higher branches, hollow bones to help it glide better, and longer feathers to channel the air).  Via these changes the organism conquers its new territory.

Professor Benton elaborates, "Competition did not play a big role in the overall pattern of evolution.  For example, even though mammals lived beside dinosaurs for 60 million years, they were not able to out-compete the dominant reptiles. But when the dinosaurs went extinct, mammals quickly filled the empty niches they left and today mammals dominate the land"

Professor Stephen Stearns, a senior evolutionary biologist at Yale University disagrees with the report's assessment that competition was less important than space in the evolutionary process.  He states, "To give one example, if the reptiles had not been competitively superior to the mammals during the Mesozoic (era), then why did the mammals only expand after the large reptiles went extinct at the end of the Mesozoic?"

While the debate is unlikely to settled conclusively anytime soon, it's interesting to note that there's a broad spectrum of ways space and competition could stack up in terms of importance. 

The new study is published in 
Biology Letters, a Royal Society journal.





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