Without qualified dissenters, progress would be much slower, and arguments would be far less robust. Greta Keller happens to be a 73-year-old paleontology and

Without qualified dissenters, progress would be much slower, and arguments would be far less robust. Greta Keller happens to be a 73-year-old paleontology and geology professor at Princeton University. And the uncharming, unprofessional name-calling? "You know you’re over the target when the flak is heaviest."