In so doing, they have reaffirmed the mechanism that Darwin first suggested in his Theory of Evolution.
Darwin’s theory says that individuals in a species pass on successful traits to their offspring. This process is called ‘deterministic inheritance.’
Over many generations, these traits become advantageous developmental trends which help the species thrive in their environment – such as the lengthening of the giraffe’s neck.
Deterministic or Random?
However, ever since Darwin formulated his theory 150 years ago, there has been dispute about whether evolution can be deterministic or is it purely random?
Believers in creationism or 'intelligent design' say evolution cannot work because it is a random process where changes occur through randomly inherited traits which are not necessarily advantageous.
For example, giraffes would not experience a common neck-lengthening; some giraffes would develop long necks, while others would develop short ones.
The collaborative study by researchers from the Technion-Israel Institute of Technology in Israel, the Department of Biology, New York University, Institut Jacques Monod, University of Paris and the Max-Planck Institute for Developmental Biology, Germany set out to test whether evolution is random or not.
The research was carried out in all these different centres to ensure that any conclusion reached would not be based on the work of just one or two researchers.
Nematodes Show the Answer
Using various techniques including DNA strand analysis and electronic microscopy, the researchers studied the development of the female sexual organ in 51 species of nematodes.
Nematodes are a type of worm commonly used to understand evolutionary processes. They have a very short life cycle compared to mammals such as giraffes, so that changes inherited over many generations can be recognised in a comparitively short period of time.
When the researchers measured changes in 40 defined characteristics of the nematodes’ sexual organs (including cell division patterns and the formation of specific cells), they found that most were uniform in direction, with the main mechanism for the development favouring a natural selection of successful traits.
“Since random development would not create such unifying trends, we concluded that the observed development was deterministic, not random,” said Professor Benjamin Podbilewicz from the Technion Faculty of Biology.
Reaffirming the Mechanism of Darwin’s Theory
Professor Podbilewicz said the team’s findings, “constitute a significant milestone in establishing and reaffirming the mechanism of Darwin’s theory”, and will help in understanding how evolution works in all living creatures.
The study, 'Trends, Stasis, and Drift in the Evolution of Nematode Vulva' is published in the November 2007 issue of Current Biology.
See also: Evolution of the Human Eye
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