Why aren't human babies considered larvae?

Question

I've seen people who are anti-baby describe babies, or children in general, as human larvae. This is generally done in order to make them seem weird. While I feel like this statement is wrong, I can't quite put my finger on exactly why.

Many definitions of "larva" specify that they must metamorphosize, or go through significant morphological changes on the path to adulthood. However, tadpoles gradually change form, rather than metamorphosizing, and hemimetabolic insects have larval instars that aren't substantially different from adults, aside from being sexually immature and smaller. "Sexually immature and smaller", of course, also describes babies fairly well.

Unfortunately, I'm no biologist and my knowledge of what defines animal young as larval vs. non-larval is rudimentary, at best, so I'm not sure if there's a more precise definition of "larva" than the one I found on wikipedia, which would disqualify human babies. What traits differentiate larva from non-larva, and which of those traits to babies lack?

Answer 1

For animals with a clear larval stage, the presence of such a stage indicates that there is a metamorphosis, a change in body morphology at some point in development.

Metamorphosis does not necessarily refer to an 'instant' transformation or one that requires a pupation step or something similar; gradual change can still be metamorphosis, as long as there is a clear 'before' and 'after.'

Human infants, on the other hand, don't go through much of a metamorphosis: sure, they grow quite a bit, but their general body plan does not change. Contrast this with insects, or your tadpole example, and it is clear there are major body plan changes from larvae to adult stages.

The Wikipedia page on larvae describes the characteristics of larvae fairly clearly. Like most traits in biology that vary across taxa, you are likely to find some intermediate creatures where the presence of a larval stage is somewhat controversial or depends on opinion. There could be a difference of opinion on how much of a change is sufficient to describe a juvenile form as a larvae. Humans don't have a postnatal stage that approaches that potential boundary.

The part in your question about people who are "anti-baby" sounds a bit judgmental, but I think what you are describing is just a phrasing meant to be somewhat humorous and to evoke images of "gross" larvae; I wouldn't take that for any biological meaning and I wouldn't focus your time on proving it "wrong" - the actual difference of opinion you have is something entirely different.

Answer 2

Children certainly are not human larvae biologically, for the reasons explained in the accepted answer.

However, calling children larvae is a metaphor that refers to child's mental and social development rather than morphological. Stepping back and looking at a kid as human larva can give adults important insight:

• A larva has entirely different needs and capabilities than imago. Adults sometimes forget that.
• Important milestones of development (walking, talking, social training, adolescence) resemble instars: behavior and needs of a kid at given milestone have little in common with needs at previous stage.
• The purpose of a larva is to molt into adult form. Which is something that many parents tend to forget: that the only purpose of their kid is to grow into a functioning adult eventually.
• Actions of the larva make no sense for the imago, and imago can't be held responsible for it's previous instar actions. That's somehow a trope for family embarrassing teens/young adults with things they've done as kids. Larva analogy helps to deal with such situations and memories.

This analogy is anti-baby only used in context against babies. In some parenting books, this analogy is used to help parents understand their children better. The only inherently bad thing about it I can think of is exploiting some people's aversion to insects in general and larvae in particular.