Unusual number of males among the 70 who went to Egypt

Question

B'reshis chapter 46 lists the seventy descendants of Yaakov who went to Egypt. It actually lists sixty-nine: let's assume Yocheved was the seventieth, as Rashi explains. It also lists (in pasuk 12) two who died before the trip down, so there are a total of 72 descendants of Yaakov listed. Of these, three are female: Yocheved, Serach, and Dina. Assuming a 50% chance of having a boy at each birth, the probability of such a disproportionate number of babies of one sex is about 0.000000000000003%. What's going on?

(And if you want to say there were females not listed (besides Yocheved), then you have to explain why the Torah says there were seventy (do the females not count?) and why it lists some females and not others. That's even if, as suggested in an answer, there are dead females not listed: the Torah lists dead males, after all.)

Answer 1

This link discusses this question at length. http://www.etzion.org.il/vbm/archive/9-parsha/13vayigash.rtf

Rash"i mentions (to answer for the opinion that there were girls born along with each of the sons of Ya'akov) that there were more females but they all died before going to Egypt. However, we are left with the implication that only those named and counted were part of the descending party. (. . which entails that all of Ya'akov's sons married Egyptian women, making it not remarkable when an Israelite man married an Egyptian woman later in the Torah, among other technical difficulties!)

Perhaps the number 70 is used not [only] as a census, but as a qualitative description of Ya'akov’s family for the purpose of comparing it in its totality to the nations of the world, which also comprise 70. (cf. D’varim 32:8-9) The reason Rash"u et al. were compelled to give an explanation for the absence of many females was that the inclusion of Dina and Serach indicated that women were being counted, despite the general rule that only males are counted when the Torah records census data. The burden of explanation is really on the inclusion of these two women, not the exclusion of all the others.

Thus, an alternative [to the null hypothesis] to explain their inclusion could be that the Torah wanted to add up to exactly 70, while fitting the pattern of each wife - Le'a and Rachel - having exactly twice the number of offspring as her slave - Bilha and Zilpa. These specific members of the family were chosen from among all the other females due to their special merits, as attested in the midrashim.

Answer 2

What's the problem? I know families with multiple generations of mostly (or all) boys. There's a family that comes to mind with something like 6 brothers who are mostly married, and there are now between 4 and 6 sons to each of those brothers. In all, the grandfather has about 24 or 25 grandchildren. If I'm not mistaken there is one granddaughter among them.

I also have family with similar rates.

It's not like it can't happen. It's just surprising, perhaps, if you live your life by statistics.

Answer 3

Male vs female is not blind 50-50%, it depends on us too. As mentioned in Niddah 31a (last line), with some effort one can make his wife to born just boys. If you see further on 31b you can see such a phrase

אמר רב קטינה יכולני לעשות כל בני זכרים

my translation: Rav Ktina told: I can make all my children to be boys.

If Rav Ktina could, I think that children of Yaakov also could make it.

Answer 4

Recent genetic studies show that male offspring tend to follow their father's trends in their own offspring. In other words, if there are a large number of males in a family, those males in turn, go on to produce a larger proportion of males to females (and the converse is true). The conjecture is that the weighting of male/female sperm is passed on to male offspring.