Reply to McGrath On The Size of Jesus’s Family

A New Testament scholar, James F. McGrath, has responded to my post on the size of Jesus’s family and it’s puzzling. As he argues,

I had this come up in connection with a blundered attempt by a mythicist (who apparently doesn’t understand what an average is) to use an estimate of the maximum family size in Iron Age I proto-Israelite settlements to try to argue that the information about the size of Jesus’ family could not be correct. Yes, seriously.

and that

I’ve argued on other grounds that Jesus’ family appears to have had some significant social status.

Where to begin?

I’m not sure if McGrath read my post correctly because he seems to think I’m using the average of 4-5.5 to show that Jesus’s family of nine or greater was impossible, when I only used it to argue that the “likely[hood]” (read: probability) of such a family was low. As someone who praised the Bayesian methodology of Richard Carrier, it’s odd that he suddenly avoids using it.

Second, McGrath mistakenly assumes that there would have been a substantial economic difference between Iron Age settlements and the early 1st-century. While this is a common mistake for most people, it’s strange hearing it from someone who is supposed to know about ancient history. Regardless, these and other issues will be addressed.

Was Jesus’s Family Average? 

Of course, this analysis is only relevant if the Jesus family were the kinds of people who lived in ordinary compounds. McGrath argues in his paper that James had the social status of a Davidic heir which would make the family above average. However, the relevant question is not necessarily their social but economic standing to support such a large family.

In the gospel account, Joseph was a Tekton (or “carpenter”) which was a specialized and sustainable job, but was not necessarily wealthy. Luke for instance gives an account of the Jesus family during the passover sacrifice, those who can’t afford a lamb, instead offer two pigeons and the Jesus family does this, showing at least that it had financial problems.

This means that Christian followers thought that while the Jesus family wasn’t necessarily impoverished, it certainly wasn’t rich either. This not-too-rich and not-too-poor is right where an average might be and thus can be used in our analysis.

How Probable Was An Average Family of 9+?

Let’s assume for the sake of argument that there was no limit to how large a family could get (an issue we’ll get back to later), how likely would an average family like this be?

The problem is that while we have estimates of averages we don’t have the distributions. It could be that while the average is a particular number, the distribution can favor a higher number, of one which is clearly not the average. For instance, in the US during the late 1700s, while the average was around 5, a plurality of families consisted of 7 or more people, which was much more likely than any other.

To offset this, I ran two distributions, one generous using the standard deviation of a population with 5 and one that’s more realistic using the standard deviation with a population of 4.5 exactly)

In the generous scenario you get p = 0.0089 or 0.89% chance of being in such a family (SD = 1.9), in the realistic scenario you get p = 0.0062 or a 0.62% chance of being in a such a family (SD = 1.8).   The bottom line: you get less than a 1% chance of being in such a family which makes it unlikely.

Generous Probability For a Family of 9+

ImageFor reference, here’s what Jesus’s family would look like if it had 6 people using an SD of 1.8, which would have a 20% chance of being likely:

Realistic Probability for a Family of 6+

ImageWas There A Limit To How Many Children Families Could Have?

Some background: a study of Israel settlements said that it was economically impossible for an average family to be larger than seven. McGrath says that it’s incorrect to use this because these were much older than the 1st century and apparently thinks it’s so obvious as to be ridiculous.

My response would be: Yes, seriously.

It’s a well held consensus that the economy has stayed the same or decreased until the mid-1800s. As Clarke (2007) put it, “the average person in the world of 1800 [CE] was no better off than the average person of 100,000 BC.” Pinker in The Better Angels of Our Nature makes a similar point about material conditions and crime. This might seem odd to many people but prior to industrialization there was virtually no economic growth around the world (although other indicators are sometimes used for well-being).

There’s also no reason to assume that family populations changed during that time. For instance, one scholar estimates that the Roman population remained at 4-5 which is the same as the Israeli settlements.

That being said, what this strongly suggests is that economic maximum amount of children (as well as the amount people actually had)  remained the same and thus an economically average biological family of nine impossible. Unless someone can show that there was a drastic economic difference over thousands of years in Israel, then this conclusion holds.

This Can All Be Tested

Perhaps the only worthwhile thing from this exchange is that all these issues can be statistically tested (and I invite people to double-check my work). When the chances of something happening are 0 to less than 1%, we are clearly dealing with something that should be rejected. As it stands, it’s much more likely that Jesus had nine or more metaphorical siblings then an unsustainable large family.