What Lenski’s Long-Term Evolution Experiment Actually Shows
37 Years. 80,000 Generations.
E. coli Is Still E. coli.
The world’s longest-running evolution experiment was supposed to prove Darwin right. What it actually showed is far more interesting.
Genetic changes tracked across 80,000 generations of E. coli in the Lenski Long-Term Evolution Experiment (LTEE) — the largest dataset of its kind in history.
In 1988, Richard Lenski launched an experiment with twelve populations of E. coli. Thirty-seven years have passed. The experiment has surpassed 80,000 generations — the equivalent of roughly 1.6 million human years.
Richard Dawkins called it “a beautiful demonstration of evolution in action” in The Greatest Show on Earth. Jerry Coyne called it “a poke in the eye for creationists.” A Veritasium video with millions of views declared it “one of the most direct demonstrations of Darwinian adaptation by natural selection you can imagine.”
So after 80,000 generations, what has E. coli become?
Still E. coli. Unchanged in every fundamental way that matters for the theory of macroevolution.
First, Let’s Correct the Misunderstanding
Evolutionists often claim that Lenski’s experiment makes creationists uncomfortable. That isn’t true.
Creationism predicts microevolution — variation and adaptation within existing genetic information — from the outset. If a Creator designed organisms with flexibility to adapt to changing environments, it follows naturally that E. coli would optimize for a glucose-limited flask. What creationists contest is not the existence of natural selection. What they contest is the claim that natural selection can generate entirely new functional information from nothing.
For macroevolution — single cell to human — to be explained, we need to observe the spontaneous emergence of new protein folds, new biochemical pathways, and new developmental programs. Lenski’s experiment has failed to show any of these. That is the heart of the debate.
The Citrate Affair
The most celebrated finding of the LTEE is the emergence of aerobic citrate metabolism at around generation 31,500. A population that could not feed on citrate in the presence of oxygen gained that ability. Evolutionists called it “the origin of a new function.” Three facts deserve scrutiny.
E. coli already metabolizes citrate. It does so under anaerobic conditions as part of its basic TCA cycle. What changed is that the repression of the citrate transporter gene (citT) under aerobic conditions was lifted. No new gene was created. An existing switch was turned on.
The identical mutation appears in as few as 12 generations under direct selection. In 2016, Van Hofwegen, Hovde, and Minnich (University of Idaho) published in the Journal of Bacteriology that when citrate was the sole carbon source, 46 independent Cit+ mutants appeared — all via the same mechanism: promoter capture of the existing citT gene. The reason it took 31,500 generations in Lenski’s lab was simply the absence of selection pressure, not the rarity of the mutation.
Delete citT, and the ability never appears — under any condition. The entire event was dependent on the pre-existing gene. Fellow evolutionary biologists John Roth and Sophie Maisnier-Patin confirmed this in a published commentary: Lenski’s “historical contingency” interpretation required reinterpretation. Creationists’ analysis was confirmed by evolutionary scientists themselves.
The 2024 Proto-Gene Discovery — A Real Breakthrough?
A 2024 analysis of LTEE genomes (Uz-Zaman et al., PLOS Biology) identified cases where previously unexpressed DNA regions had begun to be transcribed and translated — so-called “proto-genes.” Some evolutionists called this “evidence of de novo gene birth.”
Two critical limitations deserve attention.
First: these proto-genes were formed primarily by recruiting existing promoters. The regulatory information was not newly created; existing regulatory sequences were repositioned.
Second: the function of these transcripts remains unconfirmed. The paper itself acknowledges this. Transcription is not the same as function. A gene requires both stable expression and a beneficial function. This study demonstrated only the first.
Scribbling a few notes on a page is not the birth of a symphony.
A Question for Evolutionists
If a completely new protein fold had appeared in this experiment, how would the evolutionary community have responded? With enormous fanfare, no doubt. It did not appear. And on that point, the evolutionary community is quiet.
Lenski’s experiment continues. Jeffrey Barrick has taken it over and continues to press forward. Perhaps something new will emerge someday, they say. But is that expectation a scientific prediction — or a statement of faith?
What thirty-seven years of experiment has taught us is this: the information inside E. coli was there from the beginning. Natural selection can filter it. It cannot create what was never there.
After 80,000 generations, the most-watched bacterium in history has adapted — but never transformed. The mechanism for macroevolution has not appeared. The information was already there.
Deep Dive — 37 Years. 80,000 Generations.
E. coli Is Still E. coli.
Read the Deep Dive
References
- Blount ZD, Borland CZ, Lenski RE. Historical contingency and the evolution of a key innovation in an experimental population of Escherichia coli. PNAS, 2008.
- Dawkins R. The Greatest Show on Earth. Bantam Books, 2009.
- Holmes B. Bacteria make major evolutionary shift in the lab. New Scientist, 2008.
- Blount ZD, Barrick JE, Davidson CJ, Lenski RE. Genomic analysis of a key innovation in an experimental E. coli population. Nature, 2012.
- Purdom G. A Poke in the Eye? Answers in Genesis, 2008.
- Van Hofwegen DJ, Hovde CJ, Minnich SA. Rapid evolution of citrate utilization by E. coli by direct selection requires citT and dctA. Journal of Bacteriology, 2016.
- Roth JR, Maisnier-Patin S. Reinterpreting long-term evolution experiments. Journal of Bacteriology, 2016.
- Uz-Zaman MH, D’Alton S, Barrick JE, Ochman H. Promoter recruitment drives the emergence of proto-genes in a long-term evolution experiment with E. coli. PLOS Biology, 2024.
- Chihoub D et al. The evolution of robustness and fragility during long-term bacterial adaptation. PNAS, 2025.
