If we could replay the history of life, would evolution turn out the same?

Partly. If we could rewind the history of life and press play again, many details would very likely come out differently. But not everything. Evolution keeps finding some of the same solutions, again and again.

The question has a famous history. In 1989, the scientist Stephen Jay Gould wrote a book called Wonderful Life. He argued that evolution is full of chance and quirky turns. If we replayed the “tape of life” from the distant past, he said, the living world would look far different from today’s. Simon Conway Morris, an Earth scientist at the University of Cambridge, argued back. He pointed to convergent evolution, when unrelated living things evolve the same kind of trait on their own. In his view, life takes many routes but reaches only a few destinations.

We cannot rewind all of life. But we can replay small pieces of it. In 1988, the biologist Richard Lenski started 12 flasks of the same bacteria, E. coli, and let them evolve side by side. By 2008 they had passed 40,000 generations. Samples are frozen along the way, so the team can go back in time and run history again.

The results show both sides. All 12 populations got better at living in their flasks, often through similar changes. But only one population evolved the ability to eat a food called citrate, after more than 30,000 generations, as a 2008 paper reported. Replays showed that it needed earlier changes first. That is chance and history at work.

Nature shows the same mix. Eyes capable of true vision arose separately several times in different animal groups. Sharp, high-resolution eyes come in different designs, such as camera eyes and compound eyes.

So the plain answer is that evolution mixes chance with patterns that repeat. That much is Established. Our overall answer, “partly,” is Supported, still debated. Whether a full replay would give a broadly similar world, including anything like us, is an Open question.