for National Geographic News
Sex is part of the "oldest profession" and is often called the subject of the "world's oldest joke." Now scientists think they've found evidence of the oldest known creatures to engage in sexual reproduction.
Nature's first sexual encounter took place among tubular invertebrates called Funisia dorothea, which lived about 565 million years ago, a new study suggests.
Paleontologists found the F. dorothea fossils in 2005 on an ancient seafloor in the South Australian outback.
The ropelike creatures were tightly packed into groups that resemble those of modern sponges and corals.
These living invertebrates use a reproductive technique that releases floating eggs and sperm to produce mass births of many offspring, called larval spatfalls.
(Read "Moonlight Triggers Mass Coral 'Romance'" [October 22, 2007].)
In a paper that appeared last week in the journal Science, the researchers argue that the way the F. dorothea fossils were found suggests they might have used the same body positions to ensure sexual success.
"We can't say 'definitely' about something that happened 565 million years ago," said Mary Droser, study co-author and professor of earth sciences at the University of California, Riverside.
"But it's very likely that this was sexual reproduction."
F. dorothea are part of the so-called Ediacaran biota, the first multicellular life-forms to evolve beyond bacteria, plankton, and algae.
The intriguing animals were common from about 580 million years ago until the start of the Cambrian Explosion about 540 million years ago, when the fossil record began to include the lineages of almost all living animals.
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