I was fascinated to see that Google’s Gemini AI system actually generated a false claim in a futile attempt to mitigate the mathematical dilemma for TENS by asserting that while the 1,600 generations-per-fixation number was correct and relevant, there were faster fixations reported in the scientific literature. This struck me as possible, but unlikely, so naturally I inquired about the specifics.
VD: The study published in Nature in 2009, Sequencing of 19 whole genomes detected 25 mutations that were fixed in the 40,000 generations of the experiment, reported fixation events taking place at a rate of 1,600 generations per fixation event. Are you aware of any specific publication reporting a faster rate of fixation, as measured in generations?
GEMINI AI: You’re referring to a key finding from Richard Lenski’s long-term E. coli experiment, a landmark study in evolutionary biology. It’s true that the average rate of fixation observed in that specific study was around 1,600 generations per fixation event. However, there are indeed publications reporting faster rates of fixation, particularly in studies involving strong selection pressures and/or microorganisms with short generation times:
Studies on Antibiotic Resistance:
Timeframe: Fixation of resistance genes can occur within tens of generations (days to weeks) in bacterial populations exposed to antibiotics. In situations with strong selection pressure and/or microorganisms with short generation times, fixation events can occur much more rapidly than what was observed in Lenski’s long-term experiment.
You keep speaking in general terms. Please provide the specific experiment or study as well as the actual rate of fixation events reported in terms of generations. Three examples will suffice.
You’re right to ask for specifics! It’s important to back up general statements with concrete examples. Here are three examples of studies reporting faster fixation rates than the 1,600 generations per fixation observed in Lenski’s long-term experiment:
- Rapid Rise of Antibiotic Resistance in Pseudomonas aeruginosa
Study: “Evolution of high-level ciprofloxacin resistance in Pseudomonas aeruginosa in a patient with cystic fibrosis” by Breidenstein et al. (2011), published in the International Journal of Antimicrobial Agents.
Organism: Pseudomonas aeruginosa, a bacterium that causes lung infections in cystic fibrosis patients.
Selective Pressure: Exposure to the antibiotic ciprofloxacin.
Fixation Rate: In this study, the authors observed the rapid evolution of high-level ciprofloxacin resistance in a patient over a period of just a few months. Given the generation time of P. aeruginosa (around 20-30 minutes under optimal conditions), this translates to fixation events occurring within tens of generations.
Key Finding: Specific mutations in genes encoding DNA gyrase and topoisomerase IV (the targets of ciprofloxacin) were rapidly selected for and became fixed in the bacterial population within the patient.
- Evolution of Drug Resistance in HIV
Study: “Rapid evolution of human immunodeficiency virus in patients receiving no antiretroviral therapy” by Shankarappa et al. (1999), published in Nature Medicine.
Organism: Human Immunodeficiency Virus (HIV).
Selective Pressure: The host’s immune system and, in some cases, the initiation of antiretroviral therapy.
Fixation Rate: This study tracked HIV evolution in patients not receiving treatment and found that mutations associated with immune escape or drug resistance could become fixed within a few years. Considering HIV’s generation time (around 1-2 days), this equates to fixation events occurring within hundreds of generations.
Key Finding: The high mutation rate of HIV, combined with the strong selective pressures exerted by the host’s immune system, leads to rapid viral evolution and the fixation of advantageous mutations.
- Experimental Evolution of Yeast under Nutrient Limitation
Study: “Experimental evolution of a metabolic pathway” by Fekete et al. (2010), published in Molecular Systems Biology.
Organism: Baker’s yeast (Saccharomyces cerevisiae).
Selective Pressure: Limitation of a specific nutrient (galactose).
Fixation Rate: This study examined the evolution of a metabolic pathway in yeast populations adapting to galactose limitation. They observed the fixation of beneficial mutations within a few hundred generations.
Key Finding: By tracking the genetic changes and the corresponding improvements in metabolic function, the authors demonstrated how new metabolic capabilities can evolve rapidly under strong selective pressure.
These examples illustrate that fixation events can occur much faster than the average rate observed in Lenski’s long-term E. coli experiment, especially in situations with strong selection pressures and/or organisms with short generation times.
(Nota Bene: I ignored the HIV and the yeast studies, since their generalities and references to “hundreds of generations” rendered them irrelevant. To be interesting, we need to see mutational fixation events in the single digits, or at most a few tens, of generations. I also assumed “just a few months” to indicate a minimum of three.)
Given the generation time of P. aeruginosa (around 20-30 minutes under optimal conditions), and the period of three months, how does this translate to fixation events occurring within tens of generations? Wouldn’t that translate to more than four thousand generations?
You’re absolutely right to question that! My apologies for the misleading statement.
You’re correct in your calculation: With a generation time of 20-30 minutes (let’s use 25 minutes as an average), there are 24 hours * 60 minutes/hour / 25 minutes/generation = 57.6 generations per day.
Over three months (approximately 90 days), this would be 57.6 generations/day * 90 days = 5184 generations. So, three months translates to thousands of generations, not tens.
In other words, despite the best efforts of AI, Darwin is still dead and TENS is still mathematically impossible. Which fact Vibe Patrol found worthy of memorializing and celebrating with the track Darwin’s Dead, which you can hear on UATV or on YouTube now, although the audio quality is definitely better on the former. Spotify and iTunes should be following soon. Who said you can’t learn science and get your groove on at the same time?
It’s not my usual metier, but then, I did come of age in Minneapolis during the Prince years. This is the Fixation Funk mix.
Get your groove on
Cuz Darwin’s dead y’all.
Math don’t lie
And that’s a fact!
Generations passing
One by one,
Fixation’s slow,
But the funk’s begun!
