The Number of Our Ancestors To the Editor of the SCIENTIFIC AMERICAN: The search for truth is said to be often of more benefit than its attainment; and I am glad to see that a solution of the problem is beginning to emerge out of darltness, thanlts to Mr. Ecltles's letter in your issue of August 21st, although it only lifts a corner of the curtain. He proves what I have thought all along, that people are far more closely related than is generally supposed, but there is another side to the problem he does not touch. Consider the five or six distinct races of manltind, and the different nations of the world; such isolated people as the Japanese, Chinese, South Sea Islanders, Eskimo, Thibetans, and many detached tribes of India, Africa, and the other continents and Islands. Must there not be thousands, not to say millions, of people living to-day who have not the least commingling of blood in their veins for thousands of years at least? Suppose we say that there are only twenty different people, a very conservative estimate, and take one from each as totally unrelated to the others for say one thousand years past, and reduce the number of their estimated progenitors (1,094 millions) to 10 per cent to meet Mr. Eckles's blood-relationship (a very generous allowance, as the isolation of groups works both ways, and tends to keep distant communities apart), and we arrive at 2,000 millions living at that date against the 1,500 millions of to-day. Los Angeles, Cal. A. K. VENNING.