The largest annual protest in the nation for over four decades, the March for Life announced its new and notable theme for 2019: "Unique from day one."

For those not following the evolution of pro-life politics, it may seem banal. But it marks an effective and strategic merger of a long-debated political issue with undeniable, scientific facts about when human life begins.

Like the concept of death, the meaning, definition, and understanding of human life has evolved over time. In Medieval Europe, a fetus was understood to be "alive" at the moment of quickening, or movement, in the womb. At this roughly 16-week mark, the soul was thought to enter the body.

But thanks to revolutions in scientific imaging and ultrasounds, we now know that we can usually discern a baby's gender by that point and that development has already come a long way. Six or seven weeks into pregnancy, an embryo's synapses are already firing. At just five weeks, an embryo has a heartbeat. At a chromosomal level, a zygote itself is already unique, with separate DNA and therefore a separate body from that of its mother.

What we definitely know about fetal development is almost as interesting as what we don't yet. Although Republicans have touted the 20-week mark as a delineation of fetal pain, scientific consensus still isn't positive fetuses can feel pain at that point. It's also fully possible that they feel pain much, much earlier.

Science has made the pro-life position not only strategically easier to defend, but also more compelling. The pro-life position no longer hinges on traditional sexual mores, but rather on the objective knowledge that, by the end of the first trimester of pregnancy, a fetus can feel someone pressing on the mother's belly and kick back, even if the mother feels no quickening yet. What's more, the notion that a pregnancy ends one's life and closes all doors is becoming outdated, as the nation's churches, employers, and institutions have become more friendly to single mothers.

The abortion debate often feels like two ships sailing past each other in a dark harbor at night, with both sides attacking each other's worst arguments and operating under the assumption of the worst possible faith.

The March for Life's new theme is scientific, but, most importantly, it's strategic to bring the debate back to a simple question: When does life begin?