Comment by nkrisc

A few years ago I tried out TikTok and quickly came to see that there are huge niches inside the platform that are barely even searchable or existent outside the app. One of which was these videos of people sprinting or galloping on all fours. It's fascinating and terrifying seeing people who've practiced do the movements, it's uncanny in both how natural and unnatural it can look. It seems to be an intersection of unconventional exercise enthusiasts and furry-types.

Sprinting: https://www.youtube.com/shorts/6S0ctkOixj8

Galloping / jumping: https://old.reddit.com/r/toptalent/comments/ldxsoz/these_peo...

I just went down a small rabbit hole, watching some videos of quadrupedal running, and what struck me was how un-balanced the motion looked. Even the guy who is (one of) the world's fastest has this weird twist in his back while he is doing it, to make sure his knees and elbows don't smack together. That may be sustainable when you are young and strong, but I worry this guy, or anyone else who gets into this, is going to be wracked with long-term damage and in a lot of pain when older.

Ryuta Kinugasa, Yoshiyuki Usami. "How Fast Can a Human Run? Bipedal vs. Quadrupedal Running." Frontiers of Bioengineering and Biotechnology 4:56 (June 2016).

That looks remarkably like an April Fool's article released at the wrong time of year. The second-to-last paragraph is where they reveal the joke to anyone who wasn't already in on it:

> This study has limitations. Although statistical models are significantly related to mathematical formula [sic], the use of a statistical model to accurately predict future athletic performance is challenging (Hilbe, 2008). Fitted linear models should be treated with some caution. The use of linear regression for world record modeling would yield a continued decline that would eventually become negative, thus suggesting that update of world records can be continued until 0 s. It must also be noted that quadrupedal world records did not exist before 2008. This relatively recent involvement [sic] of quadrupedal running results in a somewhat tenuous comparison of world record times. Therefore, despite a high coefficient of determination, a large diverging confidence interval was found.—

—and then right back into it—

> —The 95% confidence intervals [sic] indicates that projected intersects could occur as early as in 2032 (9.238 s) or as late as 2076 (9.341 s).

A "rebuttal paper" might accept their major premise (i.e. feasibility of "a statistical model to accurately predict future athletic performance") but argue that rather than fitting a straight line (linear regression), we should fit an exponential decay curve (exponential regression). In an appendix, we'd try fitting a hyperbola (y = K1/(x-X0) + K2), taking X0 for quadrupedal running at 2008 and X0 for bipedal running anywhere from 2 million to 10 million years ago.

In an alternative "experimentalist approach," the rebuttal paper's author would actually run 100m himself, first on two legs and then on four; plot these as an additional data point (with x=2025) in each set; and fit a polynomial to that data. This would likely change the conclusion quite drastically. ;)

I’m going to wait and see with that one.

To be precise though the species is called Ursus maritimus and it is often considered a semi-aquatic species rather than just a terrestrial mammal.

I had no idea how enormous moose were until I had to go to Fairbanks a few years ago for a work thing. It was unreal sitting in line waiting to move through the gate at the air base and seeing a moose casually running down along the 8 foot fence along the perimeter and realizing it was taller than the fence!

I would definitely consider beavers to be at least partially aquatic, considering they lodge in aquatic environments and need to live near water.

That doesn’t surprise me though, considering our ancestors and almost all of our closest relatives are arboreal. We are descended from climbers. Our lack of climbing ability relative to other primates makes us the odd ones out.

> The dynamism of the human body is why we thrive in so many environments.

I'd say it's our hand to make tools, our brain to plan, and out throat/mouth to communicate