(Click to enlarge)
These two acorns are from the same "species" of oak. I love how books like Oaks of North America try to give, for each species, a range of the number of acorns per KG (in the case of one of these it's more like acorn per KG) When the range spans 3 or 4 orders of magnitude it starts to become somewhat unhelpful in identifying or classifying a given species.
I've said before and I'll keep saying it. We've had 6,000 years to turn corn into the planet killing soil wrecker it has become. Just think if we had devoted 1/1,000,000th of that time and energy into selectively breeding oaks for food production! Give me this kind of genetic variation and 6,000 years and I'll give you acorns the size of watermelons that tap dance and whistle Dixie.