Another great example of evolutionary wonders in birds is the albatross. They have a tendon sheath that allows them to lock their wings open. This, combined with their giant wingspan, their relative heft (albatrosses are porkers), and some mysterious sensory mechanism and they are able to take advantage of wind gradients to perform a maneuver called "dynamic soaring", wherein the bird extracts energy from the wind. Scientists have measured the heartrate of soaring albatrosses, and found it to be not much higher than their resting heart rate. Albatrosses use this advantage to journey thousands of miles across the pacific, without landing once.<p>Some more info:<p><a href="https://en.wikipedia.org/wiki/Albatross#Morphology_and_flight" rel="nofollow">https://en.wikipedia.org/wiki/Albatross#Morphology_and_fligh...</a>
That was a lot of explanation about how the joints lock into place, but that's not what's interesting to me. If I took a steel rod and put a stuffed animal at the top of it, I wouldn't expect it to be inherently stable.
The reason anything with two legs is more stable on one foot is that it has the choice to immediately put the free foot anywhere in order to bring about stability.<p>I have taught this to hikers who were struggling to get over some obstacles such as boulders. Quit standing on both feet and teetering. Always keep one in the air. When you step onto the next rock, lift the recovering foot, and keep it up until you decide the next step.
A much better write up of this, from one of the people who actually worked on it, was posted the other day: <a href="https://theconversation.com/neuromechanics-of-flamingos-amazing-feats-of-balance-78160" rel="nofollow">https://theconversation.com/neuromechanics-of-flamingos-amaz...</a><p>And the HN discussion: <a href="https://news.ycombinator.com/item?id=14408786" rel="nofollow">https://news.ycombinator.com/item?id=14408786</a><p>The Atlantic story linked here dumbs it down quite a bit.
Heh... Interesting article.<p>I have a standing desk, and oddly enough, find it much easier to stand on 1 leg than 2. If it didn't take effort to keep my second leg up (in the yoga pose) I could see standing like that for hours. My knee joint locks, and I keep my balance easily with the support of the desk. For some reason, standing on 2 feet is far less comfortable and requires more 'effort'.
This article reminded me of a hiking skill I never mastered - the Rocky Mountain Rest Step (the name I learned it by, but I have heard others). It's pretty simple - when hiking on steep slopes, especially with weight (a heavy pack), you train yourself to lock your knee when stepping up to conserve energy and "rest". I always found it rather uncomfortable, but I have climbed with many strong mountaineers who swear by it.<p><a href="http://rockymountainhikingtrails.blogspot.com/2012/09/learning-rest-step.html?m=1" rel="nofollow">http://rockymountainhikingtrails.blogspot.com/2012/09/learni...</a>
> "We really wanted to do an experiment where we just walked over and gave them a little prod," says Chang. "But the zoo wouldn’t let us."<p>This is _hilarious_.
TL;DR (quoted from the article):<p>"When a flamingo shifts onto one leg, two things happen. First, the leg inclines so that the foot moves from being directly under the hip to being directly under the center of the body. Second, the center of mass moves to just in front of the flamingo’s (hidden) knee, so its body weight naturally pulls the hip and knee forward. These two changes, combined with gravity’s pull and the shape of the leg bones, keeps all the joints in place."