Evolution’s ‘Big Bang’ Does Not Conflict With Darwin’s Theory, Say Researchers
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Brett Smith for redOrbit.com – Your Universe Online
While most people consider Charles Darwin the father of evolutionary theory, even the great English naturalist himself questioned aspects of his theory based on certain elements of the fossil record.
A new study from a team of English and Australian researchers explores one major flaw in Darwin’s theory backed by fossil evidence – the so-called ‘big bang’ of evolution that took place during the Cambrian explosion period between 540 and 520 million years ago.
“The abrupt appearance of dozens of animal groups during this time is arguably the most important evolutionary event after the origin of life,” said study author Michael Lee of the University of Adelaide’s School of Earth and Environmental Sciences.
According to Darwin’s theory, evolution occurs at a relatively steady pace over a long period of time.
“These seemingly impossibly fast rates of evolution implied by this Cambrian explosion have long been exploited by opponents of evolution,” Lee said. “Darwin himself famously considered that this was at odds with the normal evolutionary processes.”
“However, because of the notorious imperfection of the ancient fossil record, no-one has been able to accurately measure rates of evolution during this critical interval, often called evolution’s Big Bang,” he added.
To look into this apparent contradiction, the research team examined the evolution of arthropods — which includes insects, spiders, and crustaceans — because they were the most diverse and prolific animals during the Cambrian period and remain so today, currently accounting for more than 80 percent of all animal species on Earth.
Using the fossil record, together with molecular dating methods, the team compared the anatomical and genetic differences between Cambrian and modern arthropods, and established a set of dates over which those differences accumulated. Their methods suggested that moderately accelerated evolution could explain the relatively sudden appearance of so many new animal species in the Cambrian fossil record, according to the team’s report in the journal Current Biology.
“In this study we’ve estimated that rates of both morphological and genetic evolution during the Cambrian explosion were five times faster than today – quite rapid, but perfectly consistent with Darwin’s theory of evolution,” Lee said. “A five-fold increase in rates of evolution would compress about 100 million years’ worth of change into about 20 million years – a relatively brief period in geological terms.”
Study author Greg Edgecombe of the Natural History Museum in London noted that many arthropods developed their signature features during this evolutionary big bang.
“It was during this Cambrian period that many of the most familiar traits associated with this group of animals evolved, like a hard exoskeleton, jointed legs, and compound (multi-faceted) eyes that are shared by all arthropods,” Edgecombe said. “We even find the first appearance in the fossil record of the antenna that insects, millipedes and lobsters all have, and the earliest biting jaws.”
Lee said those game-changing evolutionary innovations opened up a whole range of new possibilities for arthropods during the Cambrian and could explain the rapid pace of evolution seen in the fossil record, adding that this type of rapid evolution often occurs when animals colonize new environments.
“When a lineage acquires a novel adaptation, they often undergo a burst of evolution, to fill up a newly opened range of environments and niches,” Lee explained. During the Cambrian explosion, this happened on a scale that is yet to be surpassed in any other era of life’s history on Earth.