Carolus Linnaeus, an eighteenth century Swedish botanist, promulgated the “binomial” naming system that egg heads use to distinguish species. Linnaeus didn’t dream the system up, but he popularized it through page-turners that he cranked out regularly (e.g. Philosophia Botanica).
The binomial system helps with nesting of species in taxonomic groups. I assume that most of my readers are Homo sapiens or have close relatives who are. The genus, Homo, has other members including Homo neanderthalensis, now represented only by a few senators. The genus is nested inside the family hominidae: the apes (including chimps, gorillas, and weight lifters). These nested taxonomic groupings usually indicate evolutionary relationships: we did not evolve from Neanderthals, but we shared a common ancestor.
The concept of species though is a tough one. If an alien archaeologist were to unearth a Chihuahua skeleton and a Doberman pinscher skeleton, why would he/she/other think they were both Canus lupus? Some biologists suggest that the ability to produce fertile offspring makes two organisms part of the same species, but many plants, and even some closely related animals can do this. There is mounting evidence that Neanderthals, and a few other species in the homo genus cross bred with modern humans.
Things can get especially muddy with cultivated plants. Kale, Brussels sprouts, broccoli, cabbage, Chinese cabbage, cauliflower, kohlrabi, Kai-lan, and collard greens are all Brassica oleracea. They are all the same species, but have been bred by humans to magnify the delicious parts (like the dogs).
I was thinking of Linnaeus earlier as I noted a wild mustard Sinapsis arvensis blooming in some untended space in my yard (pictured, yellow). Note how much those cute flower heads look like miniature broccoli. These plants are in the same family, the Brassicaceae.
Looking at these plants it’s easy to see the family resemblance. It’s like they all have the same recessed chin that Great Aunt Gertrude had. One can envision how at some point in the past they came from an ancestral population that had the potential to become both of these plants (and many others). Yet now the mustard is a noxious weed and broccoli is a delectable addition to any meal. Oddly, the best way for a plant or an animal to survive humanity’s planet destroying urge is to be tasty.