Media Release

advertisement
Marketing and Communications Office
Function Centre
GPO Box 2100
Adelaide SA 5001
Tel: 08 8201 5768
Fax: 08 8201 3027
Mobile: 0478 322 906
[email protected]
www.flinders.edu.au
CRICOS Provider No. 00114A
MEDIA RELEASE
***STRICTLY EMBARGOED UNTIL MONDAY, OCTOBER 20, 3:30AM ACDT
(4AM AEDT)***
EXTRAORDINARY FOSSIL FIND –
ORIGIN OF MATING BY COPULATION
A profound new discovery announced in Nature today (October 19) by world-renowned
palaeontologist, Flinders University Professor John Long, reveals how the intimate act of
sexual intercourse first evolved in our deep distant ancestors.
In one of the biggest discoveries in the evolutionary history of sexual reproduction,
Professor Long has found that internal fertilisation and copulation was invented by
ancient armoured fishes, called placoderms, about 385 million years ago in Scotland.
Placoderms, the most primitive jawed vertebrates, are the earliest vertebrate ancestors of
humans.
Published in Nature – the world’s leading science journal – the discovery shows that male
fossils of the Microbrachius dicki, which belong to the antiarch group of placoderms,
developed bony L-shaped genital limbs called claspers to transfer sperm to females; and
females developed small paired bones to lock the male organs in place for mating.
Measuring about 8cm long, Microbrachius lived in ancient lake habitats in Scotland, as
well as parts of Estonia and China.
As the paper’s lead author, Professor Long, who is the Strategic Professor in
Palaeontology at Flinders University in South Australia, discovered the ancient fishes
mating abilities when he stumbled across a single fossil bone in the collections of the
University of Technology in Tallinn, Estonia, last year.
The fossils, he said, symbolise the most primitive known vertebrate sexual organ ever
found, demonstrating the first use of internal fertilisation and copulation as a reproductive
strategy known in the fossil record.
“Microbrachius means little arms but scientists have been baffled for centuries by what
these bony paired arms were actually there for. We’ve solved this great mystery because
they were there for mating, so that the male could position his claspers into the female
genital area,” Professor Long said.
“It was previously thought that reproduction spawned externally in water, and much later
down the track in the history of vertebrate evolution,” he said.
“Our earlier discoveries published in Nature in 2008 and 2009 of live birth and copulation
in placoderms concerned more advanced placoderm groups. Our new discovery now
pushes the origin of copulation back even further down the evolutionary ladder, to the
most basal of all jawed animals.
“Basically it’s the first branch off the evolutionary tree where these reproductive strategies
started.”
In one of the more bizarre findings of his research, Professor Long said the fishes
probably copulated from a sideways position with their bony jointed arms locked together.
“This enabled the males to manoeuvre their genital organs into the right position for
mating.
“With their arms interlocked, these fish looked more like they are square dancing the dose-do rather than mating.”
Flinders Postdoctoral Research Fellow Dr Brian Choo, a co-author on the paper, said the
discovery signifies the first time in evolutionary history that males and females showed
distinct differences in their physical appearance.
“Until this point in evolution, the skeletons of jawed vertebrates couldn’t be distinguished
because males and females had the same skeletal structures,” Dr Choo said.
“This is the first time in vertebrate evolution that males and females developed separate
reproductive structures, with males developing claspers, and females developing fixed
plates to lock the claspers in for mating,” he said.
The discovery highlights the importance of placoderms in the evolution of vertebrate
animals, including humans, Professor Long said.
“Placoderms were once thought to be a dead-end group with no live relatives but recent
studies show that our own evolution is deeply rooted in placoderms, and that many of the
features we have, such as jaws, teeth and paired limbs, first originated with this group of
fishes.
“Now, we reveal they gave us the intimate act of sexual intercourse as well.”
Dr Matt Friedman, a palaeobiologist from the University of Oxford, UK, described the
discovery as “nothing short of remarkable”.
“Claspers in these fishes demand one of two alternative, but equally provocative,
scenarios: either an unprecedented loss of internal fertilisation in vertebrates, or the
coherence of the armoured placoderms as a single branch in the tree of life,” Dr
Friedman, who was not involved in the study, said.
“Both conclusions fly in the face of received wisdom, and suggest that there is still much
to discover about this critical episode in our own extended evolutionary history.”
2
The research involved a team of collaborators from Australia, Estonia, the UK, Sweden
and China, who scrutinised a vast number of fossil specimens held in museum collections
across the world.
***The fossil specimens of male and female Microbrachius fossils will be unveiled
for the first time at a media conference hosted by The Australian Science Media
Centre this Friday (October 17) at 10am ACDT (10:30am AEDT) in the boardroom of
The Science Exchange, 55 Exchange Place, Adelaide. Interviews with Professor
Long and Dr Brian Choo, and the debut screening of an animation, will also be
available. The fossil specimens will be placed on public display in the foyer of the
South Australian Museum from October 20. The media conference is under strict
embargo until Monday, October 20, at 3:30am ACDT (4am AEDT)***
Further information:
Name: Professor John Long, Strategic Professor in Palaeontology, Flinders University
Phone: +61 8 8201 2267 or 0408 148 660
Name: Emily Charrison, Marketing and Communications Office, Flinders University
Phone: +61 8 201 5768 or 0478 322 906
Name: Dr Joseph Milton, Senior Media Officer, The Australian Science Media Centre
Phone: +61 8 7120 8666
3
Download