What does this equation mean?

where w is body weight and A is a taxon-specific growth constant; most mammals run at a constant of about 1, but “the mean primate value for A is about 0.4” [ 3 ] . Primates grow slowly relative to other mammals of the same size to begin with, and humans, on the same equation, grow slower still during middle childhood than even that primate baseline would predict, while gaining weight faster than juvenile chimpanzees do at ages 5 to 10 in absolute terms — 2.6 kilograms a year against 1.6 for chimpanzees over the first five years, reversing to 2.1 against 2.5 kilograms a year for chimpanzees between ages 5 and 10 [ 3 ] . Slow, uneven growth by primate standards, early weaning, late first birth, and a long tail of survivors who are done reproducing: that is the package the rest of this article is trying to explain, and it is expensive enough, in strict energetic terms, that “somebody has to be paying for it” is not a metaphor. It is the actual argument on offer three different ways.