Humans should thank ancient Scottish fish fossils for joy of sex

LONDON (Reuters) - Scientists studying fossils
have discovered that the intimate act of sexual
intercourse used by humans was pioneered by
ancient armored fishes, called placoderms,
about 385 million years ago in Scotland.
In an important discovery in the evolutionary
history of sexual reproduction, the scientists
found that male fossils of the Microbrachius
dicki, which belong to a placoderm group,
developed bony L-shaped genital limbs called
claspers to transfer sperm to females.
Females, for their part, developed small paired
bones to lock the male organs in place for
mating.
Placoderms are the earliest vertebrate
ancestors of humans.
"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," said John Long, a paleontologist at
Flinders University in South Australia who led
the research.
This new finding, he added, shows that "they
gave us the intimate act of sexual intercourse
as well".
Matt Friedman, a paleobiologist from Britain's
Oxford University who was not involved in the
research, described its findings as "nothing
short of remarkable" and said they suggested
much more could be learned from the fossil
fishes.
Long, whose study was published in the journal
Nature on Sunday, 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 research then involved scientists from
Australia, Estonia, Britain, Sweden and China,
who analyzed fossil specimens from museum
collections across the world.
These demonstrate the first use of internal
fertilization and copulation as a reproductive
strategy known in the fossil record.
Measuring about 8 centimeters (3 inches) in
length, Microbrachius lived in ancient lake
habitats in Scotland, as well as parts of Estonia
and China.
Long explained that "Microbrachius" means
little arms, but said scientists have been baffled
for centuries by what these bony paired arms
were actually there for.
"We've solved this great mystery," he said.
"They were there for mating, so that the male
could position his claspers into the female
genital area."
In one of the more bizarre findings of the study,
Long said the fishes probably copulated from a
sideways position with their bony jointed arms
locked together making them look more as if
they were square dancing than having sex.
"This enabled the males to maneuver their
genital organs into the right position for
mating," he said.