Category Archives: Chapter 6 Margin Notes

Today’s discoveries and discussions about the anthropology of a million years ago.

The ape-man that never was

If you know where to look, the internet has some very interesting bookshelves, like the basement of a dank library.  I don’t even remember what I was researching recently, when I found myself browsing through the 1921 textbook, “Readings in Evolution, Genetics, and Eugenics” by Horatio Hackett Newman (I swear I’m not making up these names).  On p. 87 (p. 113 of the copy) is this sketch of “The Java ape-man, Pithecanthropus erectus.”  I knew that Java Man had originally been called Pithecanthropus erectus and later reclassified as Homo erectus, though I had never quite understood why.

Now, I’m no paleontologist, but I have been researching Homo erectus quite a lot lately, and I could spot in a moment that this skull didn’t look right.  And what was that dashed line?  Two major facial features didn’t make any sense.  Look at those canines!  (C, below)  Those are “honing” canines.  Chimps, gorillas, and other apes have them, but our hominin ancestors lost them at least 6 million years ago.  What were they doing here on a Homo erectus less than a million years old?  Second, where is his nose?!  Homo erectus had a projecting nasal bone like we do.  This representation shows a concave nose like an African ape (N).  Even for an armchair paleoanthropologist like me, these features stood out as oddly as if someone had drawn a tail on a modern human.     

It occurred to me that the face must have been a guess.  The dashed line was probably a fracture (F below).  If Eugene Dubois, the scientist who discovered Java Man, had only the skullcap to work with, then he would be impressed by the oblong skull (O) and the heavy browridge (B).  These are definitely ape-like (chimp / gorilla) features.  It would only be logical for Dubois to assume — falsely, as it turns out — that the rest of the face was ape-like too.

Not much later, by chance, I happened upon a photograph of the Java Man skull.  Here it is.  The break is shaped a little differently, but indeed, it’s only the skullcap!Dubois was especially perplexed to find this skullcap with an upright thigh bone.  That’s why he named it Pithecanthropus erectus, “erect ape-man”.  He was envisioning creatures like you’d see on “Planet of the Apes”.  Later discoveries revealed the mistakes, and this species was reassigned to Homo, the human genus.  The resulting term Homo erectus, “erect human”, is redundant and does not describe anything special.  Like non-honing canines, we now know that erect bipedality goes back to the very first hominins.

I am interested in the history of ideas as well as the history of reality.  That’s why I found it such a thrill to discover this rare textbook illustration reminding us of yester-century’s forgotten assumptions.

For further reading, I discuss hominin evolution in Chapter 7 of this website-book.

Chapter 6 covers early humans, including Homo erectus.

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Logic Problems involving others’ minds


Sometimes to solve a puzzle you must think about what other people are thinking. In fact, the very skill of logic could have served the evolutionary function of outsmarting others.

Many scientists believe that the evolutionary purpose of logical thinking is to outsmart other people.  This Christmas vacation, my family was mulling over a logic puzzle that requires thinking about what other people do or do not know, and what they can or can not figure out based on their knowledge.  I realize that this problem has two forms, easier and harder, but they both involve the same backstory, something like the plot to the opera Turandot:

Prince Peter travels to a nearby kingdom to ask the king for the princess’s hand in marriage.  Unfortunately, two other princes are also there to make the very same request.  The king takes advantage of the competition to marry his daughter off to the smartest prince; he pits them against each other in a battle of wits.  The king seats the princes at a round table and blindfolds them.  “I have five hats,” he tells them.  “Three of them are white, and two are black.  I am placing one hat on each of your heads, and I will hide the other two.”  As he does so, he tells the princes that he will shortly remove their blindfolds.  “The princess will go to the first prince to correctly identify the color of his own hat,” he explains.  “If you guess incorrectly, I will kill you.  If you cheat by looking at your hat directly or in a mirror, I will kill you.  Don’t answer until you have correctly surmised the color of your own hat!”  He then has his assistants remove the blindfolds simultaneously.  The princes look at each other’s hats.  None of them offers an answer for several minutes.  Finally, Prince Peter laughs with delight.  “Of course!” he cheers.  “My hat is _______________ !!”  He and the princess live happily ever after.

The hard version of the question leaves off here, and simply asks, “What color was Peter’s hat, and what colors were the other princes wearing?”  You can try your hand at this question first, and if you’re stumped, peek at the clue in the easier version.

To view the clue, highlight the blank area below this line:

The “easier” (but still hard) version of the question adds, “Prince Peter saw that the other two princes were both wearing white hats.  What color was Peter’s hat?”

In order to arrive at the answer to this question (which I’m not going to post today), we have to give some thought to what the other princes would know / think, and how they would react, if they saw certain colors.  We have to assume that the princes are acting rationally (because of the high price for random guessing) but that the others have either less information or less intelligence than Peter.


This problem reminds me of a moment when I was listening to the radio at about age 12.  The DJ announced that he would award a cash prize to the 10th caller.  My first thought was, “If I wait enough time for nine people to call, then I can call and be the tenth.”  But then I realized, “Wait a minute.  Everyone else will be playing by the same strategy!  They are all going to wait and try to be the 10th caller.  Since nobody will even start to call for ten minutes, I’ll wait for 20.”  This turned into an infinite regress: “But wait.  Everybody will think the same thing again, so they will all wait 10 minutes longer, so I should delay longer … on and on to eternity!”  I wondered how this game could possibly be won.  I was flabbergasted when the song ended four minutes later and there was already a winner!  People had rushed to call!  That wouldn’t make any sense unless they hadn’t thought it through — or unless they knew that at least nine other players wouldn’t think it through.  I learned that sometimes to win a game, you have to be irrational or to assume that you are playing against unintelligent or irrational competitors.


Finally, we come to the hardest logic problem I have ever heard.  In this problem, the rules are that each player is infinitely intelligent (but not clairvoyant).  The judge selects two different natural numbers, m and n.  (The natural numbers are the counting numbers:  1, 2, 3, 4, 5, …).  The judge reveals the numbers’ sum (m + n) to Player 1, and he gives their product (mn) to player 2.

“I do not know what the two numbers are,” says Player 1.

“Neither do I,” says Player 2.

“Oh, then I do know what the two numbers are!” says Player 1.

“Then so do I!” says Player 2.

What are the two numbers?

In an ideal world, I won’t have to reveal the answers to these puzzles because someone else will in the comments below.  Is that a rational assumption?  😛

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