It was predicted that humans are descended from creatures that could do this, and that we had lost this ability. When human DNA was studied, scientists found a gene which is just like the Vitamin C gene in dogs and cats. However, our copy has been turned off. This challenge has not been met. In the ensuing 140 years, no such thing has been found.
Plants give away nectar and fruit, but they get something in return.
Now, evolution says that nectar isn't free. Creatures that drink it pay for it, by carrying pollen away to another orchid. For that to happen, the creature must rub against the top of the spur. So, Darwin concluded that the spur had evolved its length as an arms race . Some creature had a way to reach deeply without shoving itself hard against the pollen-producing parts.