Tasting a plant would tell us if it was for good or ill. Humanity had managed a superior science. We had managed to harness and create fire. Humans had developed tools for hunting, nets and clubs and spear-points. We shared this level of science with our cousins, Neanderthal and Habilis.
Horses have asses and zebras for cousins.
These are close enough to produce offspring. Humanity has, well, only humanity. Breed an ass or zebra to a horse and one will have an offspring. The same is true for tigers and lions, dolphins and porpoises. All these combinations will produce an offspring that will never produce offspring.