That "constellation of cognitive abilities"

In the last post, I went to a bit of trouble, and a few re-edits, to try to phrase a couple of notions carefully, particularly the "constellation of cognitive abilities" part. I was trying to strike a balance between to key facts about human minds:

• On the one hand, we are unquestionably unique in our cognitive abilities. Perhaps the easiest way to see this is in our effect on the physical world. No one else builds paved roads, skyscrapers, or spaceships ... or needlework, or miniature ships in bottles, or pianos, or cans of preserved foods, or any of a seemingly limitless range of physical objects. Our effect on the physical world isn't just large -- in fact, for most of our existence it wasn't particularly large -- but almost endlessly varied.
• On the other hand, many, though not all, of our cognitive abilities can be found in other species, if not always to the same degree. This includes fundamentals like recognizing objects in the world and remembering where they are, or planning a route from point A to point B, but also things that may seem more uniquely human, like tracking kinship relations or recognizing that the animal in the mirror is actually you.

Focusing too much on one of these discounts the other. If we focus too narrowly on our uniqueness, we may miss things in common that could help us understand ourselves, and other animals, better. If we focus too much on analogues of our behavior in other animals, we may underestimate the degree to which are minds are truly unique.

Thus "constellation of cognitive abilities": We may share many abilities with other animals, but the combination is unique, and so is the effect of that combination.

To be sure, all species comprise a unique set of features. That's one way of defining a species to begin with. Again, it's the combination, not the individual features, that distinguish one species from another. Several other species have opposable thumbs. Many other species are habitual bipedal. Many species have hair and nails. Only humans have all three traits.

This older idea of species as a unique collection of traits can run into difficulty in the real world, which is why it has been largely superseded by the idea of a clade, that is, all and only the descendants of a particular common ancestor. A person born without hair is still fully human. Biologically, they are part of the same clade as everyone else, even if they lack what is generally considered a defining trait of mammals in general and people in particular.

In practice, while the definition of a species as a collection of defining traits and the definition of a species as a particular type of clade can sometimes give conflicting answers, they generally line up very well. Evolutionary theory is about the why and how of that alignment (among other things).

I think what I'm really pushing back against here is that the idea that some particular thing, like the ability to speak or to form complex plans or to reason about what someone else might be thinking, is the thing that makes us human, or that we became human when we reached some particular milestone.

Some features are universal to humans. We're all composed of cells, We all breathe oxygen, and we can all choke on our food because of the way our airway and esophagus are laid out. Some features are unique to humans, even though not everyone has them. For example, only humans digest lactase into adulthood, but only about a third of the population can actually do this. Some small set of features, including the layout of our airway but none of the others I just listed, is both unique and universal to all living people.

But even if there weren't any such traits, even if every particular trait we all shared was found in other animals, and every particular trait that only humans had was only found in some of us, there would still be such a thing as a human and we could still define a clade of human beings. In my view, it's more important and interesting to study the combination of traits that make us who we are, and how they interrelate, than to try to find humanity in any particular one of them.