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Grafting pieces of pig testes into mice and turning them into pig sperm factories helps fertility researchers to understand process of spermatogenesis, which as yet cannot be done in a test tube. The gene that shows human speech is a relative recent evolutionary development. The ethics of science in the fight against crime, such as DNA profiling. Why scientists should publish failed experiments with "negative results". What does the increase in parasitic liana vines in the Amazon mean?