http://phys.org/news/2013-09-biologists ... n-big.html (http://phys.org/news/2013-09-biologists-evolution-big.html)
QuoteA new study led by Adelaide researchers has estimated, for the first time, the rates of evolution during the "Cambrian explosion" when most modern animal groups appeared between 540 and 520 million years ago.
The findings, published online today in the journal Current Biology, resolve "Darwin's dilemma": the sudden appearance of a plethora of modern animal groups in the fossil record during the early Cambrian period.
"The abrupt appearance of dozens of animal groups during this time is arguably the most important evolutionary event after the origin of life," says lead author Associate Professor Michael Lee of the University of Adelaide's School of Earth and Environmental Sciences and the South Australian Museum.
These seemingly impossibly fast rates of evolution implied by this Cambrian explosion have long been exploited by opponents of evolution. 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.
"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."
The team, including researchers from the Natural History Museum in London, quantified the anatomical and genetic differences between living animals, and established a timeframe over which those differences accumulated with the help of the fossil record and intricate mathematical models. Their modelling showed that moderately accelerated evolution was sufficient to explain the seemingly sudden appearance of many groups of advanced animals in the fossil record during the Cambrian explosion.
The research focused on arthropods (insects, crustaceans, arachnids and their relatives), which are the most diverse animal group in both the Cambrian period and present day.
"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. 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." says co-author Dr Greg Edgecombe of the Natural History Museum.
To me it would indicate a set of conditions that amounts to a "perfect storm" of evolutionary environment- the right conditions and circumstances come together to create a plethora of new forms. I've never read anything that said evolution worked at a constant pace- natural selection is advantageous and favors obviously successful mutations, it doesn't have to happen at a predictable rate.
I'm waiting for someone to come in and say, "Well, God was obviously speeding up evolution during that time."
I hate it when I see creationists use the Cambrian "explosion" as if it was near-instantaneous and not on a geologic timescale.
Between this and the Big Bang, they sure are fond of explosive metaphors.
Quote from: "Hydra009"I hate it when I see creationists use the Cambrian "explosion" as if it was near-instantaneous and not on a geologic timescale.
40 million years in the history of the Earth is only about 1% of its age. A relatively short amount of time geologically but I agree creationists make it appear as if it happened over a weekend. But remember they think the entire universe was made in a few days so they exhibit being severely timescale challenged.
I dislike the term explosion to begin with, because the so-called rapid evolution took place over millions of years, just much faster than previously. I do not think it odd that such a thing occurred. I grew up in a desert/semiarid environment, and I know how suddenly a desert can bloom when the temperatures are right and the spring rain comes. I don't think it all that different- conditions developing slowly then the right trigger mechanisms set off a more rapid series of changes. It's never been problematic with me, but I'm a supporter, not a critic.
Plus, there's the sneaking suspicion that there's more to the late precambrian than we know, but it simply wasn't preserved in the fossil record as readily because tiny, soft-bodied species tend to not fossilize as readily as larger, hard-bodied species.
The precambrian tends to get underemphasized (from the way creationists talk about it, you'd get the impression that nothing at all was evolving prior to the cambrian).
In reality, the precambrian had its share of rapid evolution, too. The changes were not quite as dramatic, but they did happen.
//http://en.wikipedia.org/wiki/Avalon_explosion
We don't know what happened back then, we know what fossilized. The Creationists' problems stem from their total lack of understanding of fossilization. There could have been 100 billion species living during the ediacaran or before that couldn't fossilize, so we'll never know about them, and their descendents would seem to have popped up from nothing.
Aron Ra did a great series on evolution. It is 2 hours long but it is worth watching as it is crammed with information:
http://www.youtube.com/watch?v=bmQZ4f9f_Yw (http://www.youtube.com/watch?v=bmQZ4f9f_Yw)