Fossil fish challenge gene theory

19 May 2005

Scientists question theory of 'evolutionary leaps' between species.

New evidence from fossil fish, hundreds of millions of years old, casts doubt on current ideas about evolutionary theory.

The research, by palaeontologists Dr Philip Donoghue of the University of Bristol and Dr Mark Purnell of the University of Leicester, appears to have solved a scientific riddle by using the fossil record to explain evolutionary 'leaps' between species.

The scientists' claim that these evolutionary 'leaps' are not real, but a consequence of ignoring the fossil record. When fossils are incorporated into the evolutionary tree, a very different picture emerges.

Dr Donoghue explained, "We consider the current picture - a view of living animals only - is seriously distorted. What appear to be evolutionary jumps are really just gaps in the evolutionary tree - dead branches that have fallen by the wayside. These branches are not 'missing links', more like 'missed' links, and when we use the fossil record to put them back in place, the vertebrate evolutionary tree looks very different."

Dr Purnell added, "The new evidence, from examining ancient fossil fish, reveals that the 'jump' between, for example, lampreys and sharks turns out to be nothing of the sort. The major changes in anatomy didn't occur suddenly, as a result of a gene doubling; they took place over 70 million years or more, through a series of intermediate, but now extinct fossil fish."

The findings will set them on a collision course with geneticists who argue that the evolution of humans and other vertebrates - animals with backbones - was driven by sudden changes in their genes.

This work, funded by the Natural Environment Research Council and NESTA, challenges the scientific theory that jumps in evolution occurred at times when gene numbers increased in animals with backbones. The larger number of genes is believed to occur through gene 'duplication' and is thought to be the reason why humans and other vertebrates are more complex.

When geneticists look at which branches of the vertebrate family tree have duplicated genes and which don't, it certainly seems that each duplication led to a sudden jump in evolution.

In the example of lampreys and sharks, one duplication event occurred sometime after the evolution of lampreys but before the evolution of sharks. Sure enough, lampreys are simple vertebrates lacking jaws, teeth and a bony skeleton, whereas sharks are much more complex animals.

Thus the evidence from living vertebrates suggests a neat pattern, with a close correspondence between gene doubling events and evolution. Indeed, the evidence seems so strong that hundreds of scientific research papers have been written about the genetics of this important evolutionary pattern.

Donoghue and Purnell disagree and have thrown down the gauntlet to geneticists, saying, "Fossil species may be long extinct, their genes having rotted away millions of years ago, but if geneticists want to say anything meaningful about evolution they must include fossils in the vertebrate family tree - they cannot simply ignore them."

Further information

Cherry Lewis
University of Bristol press office
Tel: 0117 928 8086
Mob: 07729 421885

Ather Mirza
University of Leicester
Tel: 0116 252 3335
Mob: 07711 927821

NERC Press Office
Natural Environment Research Council
Polaris House, North Star Avenue
Swindon, SN2 1EU
Tel: 01793 411561
Mob: 07917 557215

Notes

1. The paper, 'Genome duplication, extinction and vertebrate evolution' will be published in the June issue of Trends in Ecology and Evolution. A PDF version of this paper can be downloaded.

Mark Purnell is a NERC Advanced Research Fellow and Lecturer in the Department of Geology, University of Leicester.

Philip Donoghue is a NESTA fellow and Lecturer in the Department of Earth Sciences, University of Bristol.

2. NERC is one of the UK's research councils. It uses a budget of about £300m a year to fund and carry out impartial scientific research in the sciences of the environment. NERC trains the next generation of independent environmental scientists. It is addressing some of the key questions facing mankind such as global warming, renewable energy and sustainable economic development.

3. NESTA (National Endowment for Science, Technology & the Arts) Established in 1998 and set up with an endowment from the National Lottery (£200m, raised in 2003 to £250m), NESTA invests the interest to support UK innovation. Since May 2000, when the programmes first opened, NESTA has spent over £58m on programmes supporting 675 awards.

Fossil fish challenge gene theory

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