First ever animals were made of jelly, not sponge
by Catherine de Lange
In the evolution of animal life on Earth, sponges have long soaked up the accolade of being the most primitive creature ever to have existed. Now it seems that their position at the very base of the tree of animal life is in jeopardy, thanks to the humble comb jelly. The finding may force us to reconsider our understanding of early animal evolution.
Unlike sponges, comb jellies (or ctenophores) have a primitive nervous system, are hungry predators and have complex cells also found in bilaterians – the group of animals, including humans, that have fronts, backs, an upside and a downside.
All animals around today split from a common lineage, about 650 million years ago. Although there is much debate about the early sequence of events, it is generally accepted that the first animals were ancestral sponges.
"When you’re learning about how animals evolved it’s always been that the last common ancestor to all living animals was probably very simple and that once the animals had a neural system and muscles they would never lose them," says Joseph Ryan at the US National Institutes of Health in Bethesda, Maryland…
(read more: New Scientist)
photo of Bathocyroe fosteri, by Marsh Youngbluth/NOAA