In response to James R and natural human instinct, let me try again to show the logic for my position.
If you look at natural selection, the choice is based on survivability and the ability to reproduce to pass forward genes. Changes in genetics that improve this, tend to be the choice of natural selection. If you have a herd of animals, the sick and weak, tend to be subject to preditors. This is part of the natural selection process, narrowing down the final choice in terms of survivability and reproduction.
In nature, this entire process of natural selection is done without artificial aids, which could allow one to slant the odds based on subjective standards. With enough rersources, humans could turn anything into the choice of natural selection, to get the result we want, since natural selection is also a product of the environment.
Let me give an example, if we had a herd of deer. Naturally, the weak are vulnerable to wolves and other predictors. The final distribution for natural selection is clear. If humans wanted to, they could say this weak deer needs to be the subjective choice of natural selection due to sentiment. We can pump in resources to assure that result, since natural selection is also environmental dependent, whether this be a natural or an artifical environment. By making the environment artificial we can alter the natural result and call it natural selection, therefore this is natural?
What I am saying about natural human instinct is based on a natural environment, without any humans slanting the odds by artificially changing the environment, so any faddish human behavior can pitched as natural. If it only pans out if we alter the environment with artificial additives to slant the odds, this is not natural behavior. Natural does not require anything but nature.
Apes can be behave homosexually, incestuous, and promiscuous without the need for humans to create an artificial environment so this can work. It is done all natural via natural selection. The same behavior in humans, needs many artificial changes to the environment, such as medical resources, to slant the odds, so we can call this natural. Natural needs no artificial to should not be subject to PC word games.
My definition of natural instinct is instinct that assures survivabilty and reproductive success, without any need for human or artificial change to the envirtonment, to slant the odds to satisfy the needs of a subjective standard so we can call it natural.
The distinction I am making is only between natural and artificial. Huimans have will and choice and can choose either, but they should also know the difference between natural and artificial.
The idea of no artificial additive to be defined as natural raisies emotional objections, such as what about the sick? I am only addressing natural human instinct in the light of choice and willpower. Sickness is not about choice and willpower. One does not choose to have cancer. Instincts do offer choice some of which are natural and others artificial requiring a slant to the environment to compensate for unnatural.