Sea sponges don't get much respect—or even much use as sponges any more—but humans and every other complex animal on the planet may owe our existence to them, according to new research. Scientists believe primitive versions of the filter-feeders, which can survive in water with very low oxygen, helped oxygenate the deep seas by consuming organic matter, creating conditions ideal for other life forms to evolve, reports Fox, which notes that the findings made sponges a good candidate to be the "Animal Eve" from which all today's creatures evolved.
"There had been enough oxygen in ocean surface waters for over 1.5 billion years before the first animals evolved, but the dark depths of the ocean remained devoid of oxygen," says the lead author of a study published in Nature. The deep oceans became oxygen-rich between 600 and 700 million years ago, with the first animal fossils dating to around 650 million years ago, and research suggests that the "first animals, far from being a passive response to rising atmospheric oxygen, were the active agents that oxygenated the ocean," he says. (Read more sea sponges stories.)