A brand new research study, conducted by a group of Adelaide scientists, suggests that there was an incredible acceleration in the rate of evolution, some 580 million years ago. This was likely to have occurred during the “Cambrian explosion,” a period in time when many collections of modern animals rapidly materialized. These findings seem to support the notion of an evolutionary “Big Bang,” a process which, according to the latest research efforts, seems consistent with Darwin’s theory of evolution.
The Cambrian Explosion
The Cambrian explosion, also known as Cambrian radiation, signifies the very rapid emergence of a significant number of animal phyla. In essence, the phyla is the grouping of organisms based upon their genetic relatedness and specialization of their body plan, which includes a myriad of physical characteristics.
Scientists have long debated the basis for the sudden appearance of these animals, some 542 million years ago, after scrutinizing detailed fossil records. Over 580 million years ago, organisms were originally very simple in design, typically involving lone cells that occasionally merged to form colony clusters. However, moving forward through time, huge diversification took place over a short period of 60 to 80 million years.
When investigating these data, Charles Darwin cogitated over this evolutionary anomaly. The illustrious naturalist claimed that this sudden and unexplained surge in the diversity of life could potentially contest his theory of evolution, which was based upon natural selection.
Many opponents of the theory of evolution have sought to exploit this area of uncertainty, calling into question the legitimacy of the phenomenon. Due to gaps in the fossil records, scientists have found it difficult to definitively prove how evolution was responsible for the radical diversity that transpired during the Cambrian explosion.
The research lead, Associate Professor Michael Lee, based at the University of Adelaide’s School of Earth and Environmental Sciences, highlights this problem:
“… 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.”
Many contemporary scientists have sought to consolidate Darwin’s theory of evolution with the evolutionary anomaly that is the Cambrian explosion. Researchers have attempted to understand what factors could cause a sudden change in the diversification of living organisms, and what it could entail with regards to the birth and evolution of animals.
The Drivers of Evolution
Indeed, a number of different factors explaining the “explosion” were put forward, including environmental, developmental and ecological factors. For example, many have suggested that low levels of molecular oxygen may have initially stunted the evolution of life. Unlike today, the earliest atmosphere of Earth had no oxygen, which is likely a prerequisite to complex biological life forms. On the other hand, modern research has implicated volcanic activity, within the oceans, as a plausible cause of accelerated evolution. It’s thought that mid-ocean ridges could have increased the levels of calcium within the waters, providing the ingredients necessary for formation of skeletal structures.
In terms of developmental theories, some scientists have sought to explain evolution based upon a shift from simple unicellular life forms to multicellular organisms. The “physics” of development were adjusted with this transition, as the genes that were originally involved in unicellular function evolved to serve a more complex function in multicellular organisms.
When exploring the influence of an animal’s ecosystem, researchers describe an “arms race” between predators and their prey. In a bid for survival, prey must change and adapt to survive predation. This is thought to be one of Darwin’s strongest theories, which is based upon natural selection.
The Adelaide research team, many of whom work for the Natural History Museum in London, investigated the genetic and anatomical variation between living animals. They then matched these changes to the timeframe over which they occurred, using a combination of complex mathematical models and fossil records.
The group specifically focused upon arthropods, which consists of insects, crustaceans and arachnids, the most diverse animal group in existence.
The researchers managed to demonstrate an accelerated period of evolution, substantiating Darwin’s theory of evolution. What they describe as a “moderate” increase in evolution could adequately explain the surfacing of advanced organisms, within a short timescale.
Their findings were published in the latest edition of the journal, Current Biology. They claim to have identified “… 4- and 5.5-fold increases in phenotypic and molecular evolutionary rates respectively…” proving evolutionary rates were much greater during the Cambrian explosion.
Dr. Greg Edgecombe of the Natural History Museum, a co-author of the study, claims the arthropod group experienced most of their evolution during the Cambrian explosion, resulting in many traits that we witness in nature today.
Their combined model, outlining genetic and anatomical changes, which appeared to undergo radical evolution around the same point in time, suggested that natural selection was indeed taking place. These animals were very rapidly changing to adapt to their ecology. The authors suggest this process was driven by competition between predator and prey, explaining the emergence of key physiological changes, including the development of exoskeletons, differences in jaw design, as well as improvements in vision and limb architecture.
During a recent press release, Dr Greg went on to state that the analyzed fossil records demonstrated the first signs of the antenna, common to insects and lobsters, as well as the very first jaws that were used for biting.
The authors maintain, despite having only studied arthropods, their results could be applicable to other animal groups, as many previous scientific observations have been successfully extrapolated for all Cambrian taxa; However, they fully accept that further research studies are required to substantiate this hypothesis.
Although these incredible results seem to support Darwin’s theory of evolution, arguably, much more scientific research will need to be conducted to convince those who challenge these assertions. It is likely, however, future scientific analysis will fill in some of the remaining gaps of our knowledge and, hopefully, will put the issue of evolution to rest once and for all.
By: James Fenner
Current Biology Journal Source