The finding that Lokis have actin tentacles adds plausibility to a eukaryogenesis scenario called the inside-out model, Spang and Schleper said. In 2014, the cell biologist Buzz Baum at University College London and his cousin, the evolutionary biologist David Baum of the University of Wisconsin, Madison, proposed an idea they had kicked around at family events: that the first eukaryotes were born after a simple ancestral cell extended protrusions past its cell walls. First these arms reached toward a symbiotic bacterium. Eventually they closed around that partner, turning it into a proto-mitochondrion. Both the original archaeal cell and the captured symbiote were enveloped within a skeleton provided by the arms.
Back when Asgard archaea were still known only from scraps of environmental DNA, Baum had asked attendees at a conference to draw what they thought the organisms would look…
