A 75,000–Generation Contrast

The Long-Term Evolution Experiment began in 1988 in California. The bacteria central to this long-running experiment – descendants of E. coli that were plucked from the wild and have spent more than 75,000 generations in captivity – now live on The University of Texas at Austin campus. 

Compare the 1980s version of these microbes with those in the lab of molecular biosciences professor Jeff Barrick in Austin today, and it’s like juxtaposing our hairy human ancestors from 1.5 million years ago, just as they’re learning to control fire, with a person living today. That’s how far evolution has carried them apart. 

The experiment began with scientists letting a single bacterium divide a few times into identical clones. The clones were placed in a sugary growth medium in flasks and put in an incubator set to human body temperature. By the next morning, the bacteria in each of 12 flasks had gorged themselves on glucose and doubled about seven times. Researchers then began a routine that has been carried out nearly every day for three dozen years now. They preserved a small sample of bacteria, and repeated their process. The LTEE became the world’s longest microbial evolution experiment – and it continues today.