If we're so different, why do we keep overlapping? When 1 plus 1 doesn't make 2

Fig. 2: Confidence intervals and comparison of 2 group means (hypothetical clinical trial data: SE_A = SE_B = 1.8, means differ by 3 SE; assuming n >> 30 and independent samples, the 2-sided p value for testing the difference in means is approximately 0.036). SE = standard error of the mean.