It would be hard to tell if a species was new, or just previously undiscovered. But, some animals have evolved in the very recent past. The Norwegian rat is no longer susceptible to warfarin-based poisons. Evolution does not favor larger organisms, and humans are losing the race. Bacteria and viruses have existed a lot longer than humans and they continually adapt, evolve and conquer. And that doesn't even include the Weaponized stupidity that the party of Trump has introduced to the human species.

https://www.science.org/doi/10.1126/science.176.4041.1343

Edit to include… I wasn't considering the domestication of animals when I gave my answer. Someone down the line brought that up.