In biology<span> and </span>genealogy<span>, the </span>most recent common ancestor<span> (</span>MRCA<span>, also </span>last common ancestor<span> LCA, or </span>concestor[1]<span>) of any set of </span>organisms<span> is the most recent individual from which all organisms in a group are directly </span>descended<span>. The term is also used reference to the ancestry of groups of </span>genes<span> (</span>haplotypes) rather than organisms. <span>The age of the </span>human MRCA<span> is unknown. It is necessarily younger than the age of both Y-MRCA and mt-MRCA, estimated at around 200,000 years, and it may be as recent as some 3,000 years ago.</span>
It was primarily the "C. United Nations" that Kennedy was addressing when calling for peace and the reduction of nuclear arms, since this was aimed mostly at the USSR.