Simplify the following text for a Grade 9 native English-speaking person.
Original: Current research has established that humans are genetically highly homogenous ; that is , the DNA of individuals is more alike than usual for most species , which may have resulted from their relatively recent evolution or the possibility of a population bottleneck resulting from cataclysmic natural events such as the Toba catastrophe .
Simplified: The DNA of individuals is more alike than usual for most species . This may have resulted from their relatively recent evolution or from the Toba catastrophe .