pulling your leg

Scientist and broadcaster Dan Riskin likes to do short videos on quirky subjects in support of his contention that Climate Change is creating many problems. His latest piece Do humans evolve in response to climate change? references a Dartmouth Study titled Ecological rules for global species distribution also predict performance variation in Ironman triathletes. That paper tries to show that athletes with longer legs do better in the running portion of Ironman events in hot temperatures, while short-legged competitors do better at cold events.

Riskin discusses body differences for rabbits in hot versus cold environments, pointing out that warm bunnies have long legs and cool bunnies have short ones. Setting out this evolutionary proof, backed by the Dartmouth Study findings, he concludes with this tepid statement:

… it reminds us that humans, like rabbits, are biological creatures affected by the heat and the cold. And we’re all in this together as we work to keep global warming to as small an increase as possible.

First of all, are the Dartmouth Study findings compelling? The author looked at 98 male and 73 female triathletes who competed in at least one hot and one cold event. The women’s results showed no long/short limbed performance differences, supposedly because the evolution of women did not involve hunting activity in the distant past.

How many of the men raced in more than 2 Ironmans? Judging an individual’s temperature performance based on just 1 warm and 1 cool run doesn’t seem like very good science.

As well, how extreme were the temperatures for the events captured in the study? They apparently took place within a temperature range of 17.78 C to 38.89 C … 39 degrees is certainly hot, but 18 degrees is pretty much the optimum race temperature.

Beyond leg length and temperature, there are a multiplicity of factors involved in the outcome of any race. Results may be impacted by terrain, tactics, pre-race preparation, nutrition, training, luck, etc. Were these significant elements considered?

Most Ironman competitions take place in warm-to-hot locales, so we should expect taller, long-legged, racers to dominate the run-section standings. Are the study findings indeed supported by the current Professional Triathletes Organization (PTO) Top-3 placings for the Ironman run category? No:

1. Jason West –  5’8”
2. Kristian Blummenfelt – 5’8”
3. Patrick Lange – 5’9”

The average height for PTO males is 5’11”, and only 3 triathletes in the run-section Top-10 are taller than that.

The Dartmouth Study findings are not compelling. It appears that both leg length and temperature are not significant for success at the highest level, where the influence of other factors (training, etc.) are likely of greater importance.

Kristian Blummenfelt is currently ranked as the #1 Ironman on the planet. His body type is long in the torso and short in the leg, and he carries a higher body mass index than others. He was featured in a Red Bulletin article that included:

Blummenfelt is putting an end to the long-held belief that long and lean is the only ideal body type for ultra-endurance sport. Both he and his coaches are quick to point out that the engine matters more than the exterior.

Blummenfelt is the 2021 Tokyo Olympic gold medalist, where he won in spite of the oppressive heat:

The scene at the finish line of the men's triathlon looked like a battlefield, with athletes seemingly overcome by the intense heat in Tokyo. – yahoo!sports

He owns the world’s fastest Ironman time ever, set in tropical Cozumel (2021). He also won the delayed 2021 Kona World Championship (moved to Utah in May 2022) in desert heat reaching 34.5 C. While only placing 3rd in the championship’s return to Hawaii later in 2022, he still broke the run-section record for that event. These are excellent results that more than balance his other performances in cooler weather.

Over the roughly 250,000 year history of homo sapiens development, global temperatures have been at least as warm as now (Roman and Medeival periods being the latest). Yet Dan Riskin asserts that a gradual 1.5 C rise in world temperature over the last 150 years is now driving our evolution. Given our air-conditioned lifestyle, why aren’t human legs getting shorter?

Even if Riskin’s position is somehow correct, is a subtle genetic change towards longer limbs a problem? It’s hard to see it as an imperative to keep global warming to as small an increase as possible.

Flimsy alarmism like this also demonstrates just how far climate science has come on its own evolutionary path towards sketch comedy.