update generation time 's annotation popsim-consortium#1312

stdpopsim/catalog/SusScr/species.py

@@ -116,12 +116,18 @@
     common_name="Pig",
     genome=_genome,
     ploidy=_ploidy,
-    # Servanty et al. (2011) on page 835 write:
-    # "Generation times were 3.6 years in the lightly hunted population and
-    # only 2.3 years in the heavily hunted population."
     # Servanty et al. (2011) on page 837 write:
     # "We Calculated generation time as the inverse of the relative elasticity of
     # the population growth rate to a change in all recruitment parameters."
+    # For comparison, Groenen et al. (2012, 10.1038/nature11622) used a best guess
+    # of 5 years (supplement page 56) and this value is cited very often.
+    # To improve upon this best guess, Zhang et al. (2022) assumed a generation time
+    # of 3 years, as the age of parents at the first litter, but pigs have
+    # multiple parities in their lifetime, so 3 years must be an underestimate.
+    # Servanty et al. (2011) seems to be the most reliable source with some
+    # concrete data, though from a lightly hunted population, so this estimate
+    # is also likely a slight underestimate, but for the deep coalescent simulations
+    # we also expect that there has been some predation in nature in the past.
     generation_time=3.6,
     # Zhang et al. (2022) on page 1045 write:
     # "... Ne of pigs (the maximum Ne was ~4x10^4; see Figure S6D) ..."