English: The number of genes inferred to have been in the Last Universal Common Ancestor some 4 billion years ago depends on the method of inference. Insisting that all phyla in Bacteria and Archaea have a gene results in just 30 universal genes. Some 11,000 genes are present in both domains, but this figure is suspiciously high, as lateral gene transfer (LGT) could very likely have brought many of them from one domain to the other. Finally, restricting the search to genes found in two different phyla in each domain, so that LGT is less likely, yields a set of 355 genes.