Biology Stack Exchange is a question and answer site for biology researchers, academics, and students. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

That for frog is 12, but what about mammalian embryos? I cannot find the exact number anywhere.

share|improve this question
I just have an intuation that the number of rounds of cleavage differ between different mammalian, since human seems to have more than 100 rounds, need to verify still from Gilbert. – Masi Feb 11 '12 at 18:16

It's not a totally answerable question, since some types of cells are going to divide more times than others. But for an estimate, take as a starting proposition that there are 1 trillion cells in the adult human body. [1] The average weight for a human is 62kg. [2] Average birth weight is about 3.4 kg. [3]

So that implies roughtly (3.4/62)* 1 trillion = 55 billion cells in a newborn.

You then take the log base 2 of 55 billion, which gives you the exponent you have to hang on 2 in order to get 55 billion, which is about 35. Then add one for that additional cell division to get from one to two cells == 36 divisions.

Of course I'm just using math, not biology, so your actual reality may vary. Certainly some cells will reproduce more often than others, maybe cells actually grow in mass instead of dividing (i.e., baby cells might have less mass than adult cells) so the baby-cell-count could be off, lots of possible sources of error.




share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.