Two signaling molecules — strigolactone and ethylene — can work independently to begin the process of leaf senescence.
Only humans understand death as the inevitable and final reality for all mortal beings no matter what we do.
If you want to see what is going so badly wrong in society, read the professional and intellectual journals.
What you’d expect is humans more or less on the level of animals — not greatly exceeding them in evil, or greatly transcending them in good.
Nowhere in the animal world do we see evil that comes anywhere close to comparing with the unfortunate depths of evil displayed by humanity.