He has published on the topics of breakup, geographic separation, infidelity, social networks, cognition, and need fulfillment and emotions in relationships.This is old science from when women relied on men financially.The v rod and z rod are both masonry tools amongst other things previously mentioned in the comments, various cycles ect.The v being a compass and z being like a spacing rule(ancient tape measure) Many of you were right in recognizing the arrows as common symbols for time, same with the serpent.
For example, by their 50’s the average male has a wife who is 10 years younger than him.
Women are delaying having children, so biologically we need younger partners. The stats you show do not account for these rapid changes that only began in the 1990's.
If you look at studies now you'll see that women have an average 9 year age range either side of their own with a preference for a small 4 years either side of their own age.
However, it doesn’t represent women’s preferences at all.
So maybe there is a kernel of truth the rule, at least for men. Le's research focuses on commitment, including the factors associated with commitment and its role in promoting maintenance.
Now that we don't need to do that we're going for younger men.