{'fraction_non_alphanumeric': 0.04590818363273453, 'fraction_numerical': 0.00998003992015968, 'mean_word_length': 4.8654970760233915, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Mutations and the age pattern of death

The age pattern of death is what biologists and demographers think about when they consider mortality (or immortality). As everyone knows, human lives on average have nearly doubled in length over the past century (1), yet human mortality still increases exponentially fast (Fig. 1) as people age past 40. Not surprisingly, the health of older people is now a major concern (2), often focused on proximate factors, biological, economic and social, that affect health (3⇓–5). However, a deeper question is, how did evolution shape the age pattern of mortality? In particular, is the rise in old-age mortality driven by an increase in the number and frequency of deleterious (i.e., bad for you) alleles? In PNAS, Wachter et al. (6) show how to compute the equilibrium distribution of deleterious mutant alleles in a large, age-structured, and genetically heterogeneous population. Their analysis is a significant advance over previous work on this question (7, 8).