What Are Your Degrees of Separation from Ancient Times?

The psychologist Stanley Milgram has pointed out that only six degrees separate everyone in the United States. Milgram was likely wrong. The number may be three or four degrees of separation. Six degrees of separation in a US population of 150 or 200 million that existed when Milgram did his work implies an assumption of everyone's knowing only 22-25 or so distinct people (there's always overlap because your neighbor knows many of the same people you do). That is because 22**6= 113,379,904 and 25**6 244,140,625. Most of us know many people casually. I have probably had close to 10,000 students in 17 years of teaching (many of my classes have been 50 to 70, and I have frequently taught summers). Likewise, a single politician like Hillary Clinton probably knows at least ten thousand people, and has probably met many more than that. So there are fewer than six degrees of separation, maybe only three. If on average we each know 1,000 then 1000**3 = one billion without taking overlap into account.

Of course, the degrees needed to reach any one of our ancestors in ancient times is greater and more difficult to compute. Part of the difficulty is that conquest dislocated people. Take the case of western Europe. There is no specific date for the fall of Rome in western Europe, but Totila and the Ostrogoths depopulated the city in the sixth century. Rome was sacked four or five times. Geiseric and the Vandals sacked Rome in 455 and Romulus Augustus, the last emperor, was deposed in 476. Alaric and the Visigoths sacked it in 410 AD and Brennus and the Gauls sacked it in 387 BC. The Arabs attacked it in the ninth century. One may guess that conquest in those days involved taking slaves.

The matter is also complicated by plagues. According to the Hacienda Pub site, "the Plague of Justinian (6th Century A.D.), the Black Death (14th Century A.D.), and the Bubonic Plague (1665-1666, which coincided with the Great Fire of London) caused an estimated 137 million dead in a world much more sparsely populated than it is today." Many in those periods lost their entire families.

So how many degrees of separation are there across generations? How many people are you removed from Julius Caesar? I would guess it takes about 80 generations to get us back to the days of Romulus Augustus (the last Roman Emperor, who was deposed in 476) and about 100 to the days of Augustus. In socialist and conservative, pre-free-market societies, life expectancy was about age 25-35. So if we figure that people died at 35 there were at least two generations alive for most at any give time.

But the world population was a tiny fraction of what it is today, even going back two centuries. Wikipedia estimates that western Europe's population was 25-30 million in Charlemagne's time, one thirty second of today's and the world's population was about 200 million, also about one thirty second of today's.

With 30 million alive at the time of Caesar, we can guess that there were no more than three degrees of separation. So My guess is that you have to go back 100 degrees to get back to Caesar, then 2-3 more laterally, so if you assume 100 down and 2-3 across there's about 200-300 degree of separation between you and Julius Caesar.

But that assumes a right triangle of relationships, vertically down through the generations and then horizontally across in ancient times. There are also "hypotenuse" relationships whereby someone you know now, knows someone from an earlier generation who was slightly closer to Caesar and the path could follow diagonally. Putting on my 10th grade geometry cap for a second (my worst subject) then if the base of the right triangle is 3 and the leg is 100 the diagonal is 3**2 + 100**2 = 10,009, the square root of which is about 100, and that would seem closer to the right answer.

I wonder if you formed a chain beginning with someone who knew Julius Caesar and ending with the person you know who is closest to Julius Caesar today, what the differences across the generations would seem like. After just a few generations the people would be quite unlike most anyone in the world today. We are much closer to people remote from us in distance than we are from the past. Yet, many people are loyal to ancient ancestors but suspicious of strangers. Of course, our ancestors are dead so do not threaten us as can people in today's world. But socially, culturally, intellectually and in most visible ways, we are more like someone who lives in China than we are like our ancestors in Roman times.