That only one in 27 males was a first-born is strange, unless there were far more girls than boys or there was an average of 27. It is true that the Midrash states that the Israelites had a very high birth rate in Egypt – six in one pregnancy (see commentaries on Ex. 1:7), but how literally should this be taken?
The question was addressed some years ago by Azriel Rosenfeld in a publication of the Association of Orthodox Jewish Scientists. He offered three possible answers:
1. If “first-born” meant first-born to the father, in a polygamous society one father may have had children by two or three wives, so it is possible that 27 children per family would not be impossibly large. However, other references in the Torah to first-born children seem to indicate that first-born to the mother is meant.
2. There may have been an unusually high mortality rate amongst the first-born. It is unlikely that Pharaoh’s decree to drown male Israelite children would have had any special effect on the first-born, but since the first-born were the leaders in worship before the Levites were appointed, many may have followed idolatrous practices and been punished by death.
Many first-born may have died after the sin of the golden calf, but a total of 3000 died at that time, and even if they were all first-born this would not explain the disproportionately small number of first-borns in the community.
3. Perhaps the “mixed multitude” (Exodus 12:38) were counted among the 600,000 (according to tradition, they adopted Judaism and converted) and they did not include first-borns since the latter were destroyed in the tenth plague. A further possibility is that the Torah’s list of first-borns was limited to males of Israelite lineage.
They are all interesting suggestions, but none is fully satisfactory. Does any reader have any other ideas?