James Watson and Francis Crick made the most significant discovery of the twentieth century: they elucidated of the molecular structure of DNA in 1953, and later shared the Nobel Prize for Physiology or Medicine for their work.
So Watson and Crick are very illustrious, to say the least. But when Watson continues to make racist statements such as this, he loses much of his credibility, and one finds it very difficult to take him seriously:
[I am] inherently gloomy about the prospect of Africa [because] all our social policies are based on the fact that their intelligence is the same as ours – whereas all the testing says not really [and] people who have to deal with black employees find this not true.
One hundred years ago, the belief that black people are intellectually inferior to whites was commonplace among scientists. The relationship between race and intelligence is still hotly debated, and remains highly controversial, but as yet no significant correlation between the two has been found.
If Watson was suffering from some form of cognitive impairment, one could perhaps excuse his statements on the grounds of diminished responsibility. But, as far as I know, he retains all his faculties, so really, his statements can only be interpreted as expressions of his prejudices.