it is only quite recently that laws and "ethics" became part of the hunting/killing jargon. Homo sapiens was a pretty exuberant killer of everything that walked the earth, including his own species, for 99.99% of his existence, beginning with spears and traps. The Chinese invented firearms over 800 years ago. The rifle was invented nearly 500 years ago. For the past hundred years we have had weapons and propellants capable of bringing down elephants or prairie dogs from long range with a single shot, with comparatively little risk to the killer. Man's early motivation for killing may have been for food, hides, bones, and protection. But with the advent of more effective and "remote" devices, we have "progressed" to killing "for sport," ie for our amusement, "showing off", and collecting the biggest and most unusual possible specimens to grace the walls of our dens and museums. Any organism of any size that stood in the way of progress, safety, ranching, farming or recreation was hunted or poisoned to local extinction, with little or no interference until the last 50 years.
Yet in all of this, there is not a single proven body, hide, bone, blood, fossil, fingernail, or even a measly hair of a bigfoot, to show for "mankind's" bloody past.