This principal was Dr. Jarvis has not ruled out any other hypothesis. Although his milk hypothesis may be a single cause for a Higher IQ, it is certainly not the only possibility. A high IQ can be related to many other things. Some examples would include, those who live in high income communities may have an higher IQ than those living in low Income communities, those who spend more time studying have a higher IQ than those who do not, and those with specific genetics may have an higher IQ than those who lack these genetics. These examples are all rival hypothesis to Dr. Jarvis’s milk hypothesis, yet he has failed to rule any out.