A helpful formulation comes from podcaster Scott Adams, of “Dilbert” fame, who comments entertainingly on the political scene.
An embryo is fully human, as is a fetus, a newborn, a toddler, a child, a teen, a mature adult and an elderly adult.
Darwinian fairy tales about prehistoric Neanderthal proclivities and modern psychology are obvious junk science.
The authors discuss the mode of preservation of Ediacaran fossils, and they document taphonomical laboratory experiments.
The oceans might be cleaner without man, but they would neither know nor care nor judge.