Ewen Callaway in Nature:
Which animals came first? For more than a century, most evidence suggested that sponges, immobile filter-feeders that lack muscles, neurons and other specialized tissues, were the first animal lineages to emerge. Then, in 2008, a genomic study pointed to a head-scratching rival1: dazzling, translucent predators called comb jellies, or ctenophores, with nerves, muscles and other sophisticated features.
That single study ignited a debate that has raged for nearly 20 years, sparking fierce arguments about how complexity evolved in animals. But after dozens of studies — some of which analysed and reanalysed the same data and reached different conclusions — the debate has become entrenched, some researchers say. “Where it might have been healthy for people to engage with curiosity and an interest in finding the truth together, it became a battle,” says Nicole King, an evolutionary biologist at the University of California, Berkeley, who co-authored a paper last November that landed cautiously on ‘team sponge’2.
More here.
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