I've been fascinated by the interactivity of Common Lisp for a while, and would really like to be able to, say, redefine functions of a running program in other languages as well. I feel like it would be extremely beneficial for debugging long-running programs.
However, I have never actually been able to program in Common Lisp without repeatedly getting to the point where it seems I have to restart the whole system. I suspect because somehow the state of the code and the state of the system got out of sync. So until now I have always given up, and used C-like languages after all, because there are more well-tested libraries available, and because I never managed to use the full potential of Common Lisp anyway.
I would really like to learn how to use Common Lisps full potential though.
It is almost impossible to show how tame the fur farm foxes on Prince Edward Island really were, but in addition to the photos - of which there are more than one [1] - there are also written reports about how tame the foxes where [2]:
"Dr. Frank, among other things at Montreal, had a pair of tame foxes lead about on the main streets, driven around in automobiles and taken to a public dance, where the girls did the fox trot with these foxes around their necks, and all this was photographed, moving pictures taken, etc., and to cap the climax Dr. Frank hired two airplanes, took up a pair of foxes in one and from the other airplane a photograph ground out several reels to be shown in the movies in the near future."
How common these traits were is another difficult question. But given that there was prior selection for tameness and that Belyaev specifically looked for those tame foxes to include in his experiment [3], it does not seem so surprising that this trait very quickly became more common.
The foxes are great proof that behaviour has a genetic component. But the change in behaviour over the course of Belyaev's experiments does not seem that remarkable. Some foxes of the initial population were already happy to approach humans and be held by them, before the experiment even started. The pictures in [1] show farm foxes from Prince Edward Island in 1922 which seem to behave extremely similar to the foxes in the youtube video you linked to.
It is doubtful, though, that the spotted fur, floppy ears, and other physical characteristics (domestication syndrome) are a result of the experiment [1]:
"The history of the Farm-Fox population undermines the commonly repeated narrative that a suite of domestication syndrome traits emerged solely as a result of selecting on tameness. There is no temporal link between most of the syndrome traits, which first appeared in Prince Edward Island (PEI) fur farms, and the later behavioral selection in Russia."
On the spotted fur [1]:
"The farm-fox breeders of PEI intentionally selected for white spotting and other unusual coat patterns (Figure 3). They noticed that crossing two white-marked foxes occasionally resulted in animals that held their heads askew, a phenomenon Belyaev would later describe in his population, suggesting shared genetic etiology. White spotting was more common in Belyaev’s selected than unselected populations, but has not been associated with less fearful behavior in individuals (Figure 2D)."
On the floppy ears [1]:
"The farm foxes of PEI occasionally had floppy ears, even as adults (Figure 3C). In the Farm-Fox Experiment, ‘delayed ear raising’ was noted (ears floppy past 3 weeks of age, but not necessarily into adulthood). While slightly more common in the selected population, the trait is extremely rare, and no association between delayed ear raising and less fearful behavior in individuals has been described (Figure 2D)."
The experiment specifically selected for behaviour, though. And the fur-farm foxes seem to have been quite tame already before the start of the experiment. Therefore, I don't find the changes in behaviour very interesting on their own [1]:
"The Farm-Fox Experiment selected for a behavioral trait that already existed in the population (Figure 3), essentially recapitulating a selection experiment performed on numerous occasions with dog breeds. [...] The change in the critical period of socialization in the selected foxes is more like the difference between more and less easily socialized dog breeds than between dogs and wolves."
There has been some doubt about the validity of this experiment [1]:
"A widespread misconception maintains that the Farm-Fox Experiment started with wild foxes and recapitulated the entire process of domestication. Belyaev himself accurately described the founders as fur-farm foxes, but by referring to the unselected population as ‘wild controls’, contributed to this misconception. In reality, the experiment started with a fox population from eastern Canada that had been captive and purpose-bred since the late 1800s, something Belyaev and his colleagues may have been initially unaware of."