Table 1.

Putative sources of early life adversity in gorillas.

			Sample size
Adverse event	Definition	Parallels in other species	Early life (n=253)	Later life (n=164)
Paternal loss	The dominant male during the individual's first year of life dies or leaves the group when the individual is <6 years old.	Humans32–34	69 35F, 34M	53 28F, 25M
Maternal loss	Mother dies or leaves the group when the individual is under <6 years old.	Humans33,34; chimpanzees7,35; multiple primates36,37; baboons6,38; elephants12; hyenas10	54 32F, 22M	50 30F, 20M
Infanticide	A group member dies by infanticide when the individual is under six years of age.	Humans34,39,40; mice41	84 40F, 44M	70 34F, 36M
Group instability	A substantial proportion of group members change when the individual is <6 years old (Jaccard similarity index of group members <0.64).	Humans33,34,42 but see43, elephants12.	49 23F, 26M	41 22F, 19M
Few age-mates	A mean of fewer than two age-mates present within the group when the individual is between two and six years old. Age-mates classified as group members within two years age difference.	Humans44; macaques45; badgers46.	48 20F, 28M	19 8F, 11M
Competing sibling	Younger sibling born when the individual is still an infant (<3.5 years)	Humans47, baboons6,38; zebra finches48.	36 26F, 10M	35 25F, 10M
Cumulative ELA	The total number of adverse events experienced in early life.	Humans1, baboons6, hyenas11	0: 85 33F, 52M 1: 67 32F, 35M 2: 51 28F, 23M 3+: 50 25F, 25M	0: 37 23F, 24M 1: 47 23F, 24M 2: 41 21F, 20M 3+: 39 22F, 17M

Sources of ELA examined in this study, their definitions, their parallels in other species, and their sample sizes. F indicates sample size for females, M indicates sample size for males. See also Table S1 for agreement between these sources of ELA.