I don't think that is it at all. It is true that people respond differently to placing themselves in harm's way, and a certain percentage of people respond positively to such situations. The minority is risk-seeking while the majority is risk-averse. But it has nothing to do with altruism. It comes about because having some individuals in a grould taking great risks can yield great rewards that the entire group by extension benefits from.
Unfortunately IMO, these opportunities are now so rare and/or socially unacceptable that those who are risk-seekers are reduced to take great risks with zero tangible rewards to satisfy their built in need for risky behavior.
Take as an example one of my favorite human enterprise ever - the Varangian traders that sailed across the river systems of eastern Europe in the 900s and 1000s AD. These guys travelled on longboats from Sweden to Constantinopel, dragging their boats over portages between different rivers, circumventing waterfalls and rapids by dragging or in some instances taking their ships apart board by board, nail by nail and re-assembling them on the other side of the rapids. Every time they came ashore they risked being attacked by wild Slavic and Turkomen tribes. This was an incredibly dangerous trip, especially in the early decades before the fortified waystations were build that took several years, and many ships did not make it. At least once an entire fleet, reputedly of as many as 200 ships, was attacked and annihilated by Pecheneg horse archers in the Crimea. If you miscalculated you'd end up going over a waterfall or being crushed in the rapids, and if you ship was sunk, or you got lost, you were hundreds of miles away from the nearest semi-civilized settlement. Good luck with that!
And once you got to Constantinopel, you then had to get back again.
I am sure that the guys who went on these trips, and either made vast fortunes on them or died trying were individuals with a similar mindset at today's thrillseekers, be they mountaineers, deep-sea divers, cave explorers or whatnot. Something at least seperated them who chose to stay at home and just farm the land.
But the difference, to my way of thinking at least, is that the Varangians, much like all adventurers and explorers of old took the risks they did with the clear goal in mind to better their lot in life and elevate their social standing by undertaking the journey, and I
