Part I: Evolution, Taxonomy, and Domestication36
The dramatic dental adaptations in African suids can there-
fore be considered as a solution to this particular problem: how
can small mouthfuls of small food items be processed efficiently
before digestion? The smaller the food item, and the smaller the
number of food items ingested at once (the size of the mouth-
ful), the less likely it is to break efficiently all the food items
with a small number of chewing cycles. The elongation of the
third molars with multiplication of cusps increase the length of
available enamel crests available for breaking small fragments
of grasses. A thin enamel also allows more numerous pillars to
be packed into the same dental surface, therefore increasing the
ratio of enamel crests to dental surface.
Herbivorous pigs display teeth that maximize the ratio of
enamel crests to the masticating surface. Multi-cuspidy, thin
enamel, and tightly packed cusps all enable a great ratio of
enamel crests length to dental surface to maximize the number
of breaking sites when masticating small elements of grass.
The specialization on small mouthfuls of short grass and the
maximization of the breaking sites enable herbivorous pigs to
break grass cells enough to digest their nutrients, which circum-
vents their lack of rumination and multi-chambered fermenting
stomach.
The height increase could represent an adaptation to the
abrasiveness of the grasses, because of its high content in exog-
enous mineral grit and silica phytoliths (Merceron et al. 2016).
Alternately, in the proposed scenario for suids, height increase
could also correspond to a strong attrition (wear caused by con-
tact between the upper and lower teeth during mastication) due
to the specialization on small mouthfuls of small food items.
The C 3 component of the herbaceous stratum during the
Neogene and Quaternary is poorly known so far. If the afore-
mentioned scenario is confirmed, and extinct suids did have a
preference for tender, short grasses and forbs, they were maybe
highly selecting C 3 herbaceous plants in the landscapes. In the
Malawi Rift, for example, extinct suids fed extensively on C 3
plants whereas C 4 grasses were present (as evidenced from their
consumption by some bovids, Lüdecke et al. 2016). Therefore,
better documenting and understanding the paleoecology of
herbivorous suids (and other herbivorous mammals with lim-
ited digestive capacities, such as cercopithecid primates of the
genus Theropithecus) could have strong implications for the
paleobiology of our own relatives, who also evolved adaptations
to herbivory (in Paranthropus) in the same landscapes.Perspectives
In the future, it will be crucial to go further than the current
analyses that are mostly limited to stable carbon isotopes and/or
basic quantification of morphology. Several methodologies will
prove extremely useful when combined with the existing data.
Additional biogeochemical proxies for paleoecology are
promising. They will be all the more informative if they are
applied to serial samples documenting the intratooth variations
corresponding to the seasonal variations in diet and environ-
ment. For example, stable oxygen isotopes (δ^18 O) are related
to the degree of water dependence of the animal and also the
local rainfall amount in tropical Africa (Harris & Cerling,
2002; Souron et al. 2012). Some major elements may be relatedto the consumption of underground storage organs of plants
(Sponheimer et al. 2005) and stable magnesium isotopes dis-
tinguish well omnivorous mammals from herbivorous ones
(Martin et al. 2015). Dental microwear, the study of the micro-
scopic scars left at the surface of the enamel facets during the
mastication of food items, discriminates fine differences in diets
(e.g. Merceron et al. 2016 for a controlled feeding experiment on
sheep Ovis aries with diets of grasses versus forbs). Recently, 3D
dental microwear texture analyses were developed and provide a
quantified way to compare the microwear features across mam-
mals (see the recent review by Calandra & Merceron, 2016).
Souron et al. (2015b) notably discriminated among extant suids
between omnivorous, mixed feeders, and grass-eating species.
Ecomorphology of postcranials, a methodology already
applied to African extant and extinct suids, could also provide
additional insights into their ecology and habitat (Bishop 1999).
The main limitation is the paucity of fossilized postcranial
remains associated with cranio-mandibular or dental speci-
mens so that they can be assigned with confidence to a taxon.
Morphological adaptations to new diets also take place at
the microscopic scale of the components of the mammalian
enamel. Microscopic bioapatite prisms are arranged in dif-
ferent ways depending on the phylogeny and ecology of the
mammals according to the biomechanic constraints sustained
during mastication. For example, the premolars of bone-
crushing hyaenids display peculiar enamel microstructures
related to their diet (Tseng 2012) and could be compared to the
premolars of Nyanzachoerus to test their function. Documenting
the changes in enamel microstructure in African suids, along
the transition from omnivory to herbivory, could explain how
extinct suids with omnivorous morphotypes (such as early
members of Pliocene Kolpochoerus and Metridiochoerus) were
able to consume large amounts of abrasive C 4 grasses.
Overall, the future of suid paleoecology is bright. Integrating
numerous complementary and independent methodologies
will without doubt allow us to better understand the timing
and rhythm of herbivorous adaptations, and the relationships
between diet, morphology, and environmental constraints.
That will allow many so far unanswered questions to be
addressed. How were the different sympatric species of herbivo-
rous suids sharing the niches? Was there competition for dietary
resources with other herbivorous mammals (ungulates, cerco-
pithecid and hominid primates, etc.) and omnivorous/carnivo-
rous mammals (e.g. hyaenids)? Which factors could explain the
lack of success of African herbivorous suids in Eurasia despite a
few limited attempts to disperse from Africa into Eurasia?Acknowledgements
I thank the editors and Cambridge University Press for invit-
ing me to contribute to this volume, and especially Mario
Melletti for his infinite patience. The ideas developed in this
review stem from almost seven years of reflections on the evo-
lutionary history of our beloved Suidae. This brainstorming
was triggered and sustained by the constant support, mentor-
ing, and stimulating discussions of Jean-Renaud Boisserie and
Tim White, as well as numerous other colleagues. I am also
extremely grateful to Jean-Renaud Boisserie for permission.00512:31:27