Sure, there are hybrids and fuzzy cases, but people of African descent generally have darker skin and curlier hair. People of Caucasian descent generally have lighter skin and thinner hair. Asians have the epicanthic fold in their eyes

Why is it utterly impossible that there be differences along the same lines, however slight, in the human brain?

Okay, some people say. Even if we accept that race is real, and that there might be some differences, it’s “racist” to broach the topic of race and IQ. Wrong. That’s like being accused of infidelity and objecting “How mean!” instead of grappling with the substance of the accusation.

Or, how about the idea that there’s no such thing as IQ? It’s fake to stick up for this one. We all casually describe one person as smarter than another. We know exactly what we mean when we call someone intelligent.

Many of us love Harvard psychologist Howard Gardner’s argument about “multiple intelligences,” where some people are “musically” intelligent, some “emotionally,” and so on.

Well, Gardner himself also stipulates “logical-mathematical” intelligence — basically what we otherwise refer to as IQ — and no one argues for pulling that one from the list.

So: IQ, or smarts, is real. Like all genetic traits, it will vary more among individuals within a group than it does among groups. However, this doesn’t rule out the possibility of overall statistical differences between the groups. Science will ultimately resolve the issue, not P.C. dismissal.

That’s not pretty. But smart people shouldn’t limit their discussion to what’s pretty.

Yet here’s the equally important point: None of this means that IQ should play a part in our discussion of immigration policies.

We should definitely make our country more inviting to high-skilled immigrants, many of which will be PhDs coming from India or China. But we cannot allow this to morph into a larger idea that humbler applicants without advanced degrees aren’t welcome, aren’t “smart enough for America.”

The Founders of the republic, after all, broached no such topic. They had their xenophobias: Benjamin Franklin got itchy about how many Germans were here in his day. But no one of Franklin’s ilk is recorded as worrying that newcomers should be systematically measured for smartness.