Notes - The Fossil Chronicles - page 211

36. This sample also included the microcephalic we used in our first study.
37. Two of the ten individuals that we accepted into our microcephalic sam-
ple had cranial capacities of 667 cm 3 and 671 cm 3 , which were slightly above our
preferred upper limit of 650 cm 3 . We decided to include them anyway in order
to increase the sample size.
38. Further details about the specimens are available in Falk, Hildebolt, et al.,
“Brain shape,” 2007.
39. We used discriminant and canonical analyses to do this, and the results
were statistically highly significant (Falk, Hildebolt, et al., “Brain shape,” 2007).
40. Because these three specimens had not been used to develop the for-
mula, it was proper to use it to classify them.
41. So much for the argument that LB1's endocast resembles that from the
microcephalic Basuto woman, which was based only on line drawings.
42. Martin 2007, 17.
43. Because little, if anything, is known about shape asymmetries in skulls
of microcephalics, we knew it would be scientifically unsound to correct the
midline of a half-endocast produced from an irregularly cut half-skull and then
use it to create a whole endocast (by mirroring the half-endocast), which would
then be used to classify the specimen.
44. Martin 2007, 18.
45. Montgomery et al. 2011. The abbreviation ASPM is for the gene called
abnormal spindlelike, microcephaly-associated. CDK5RAP2 is the abbreviation
for cyclin-dependent kinase 5 regulatory subunit-associated protein 2.
46. Thompson et al. 2001.
47. It is important to emphasize that this hypothesis does not equate mod-
ern microcephalics with fossil hominins. The products of genes frequently
contribute to a myriad of functions (known as pleiotrophy), in which case a
mutation associated with a pathology, such as microcephaly, is likely to be dis-
ruptive in numerous ways, in addition to arresting brain growth. Some of the
more obvious manifestations, however, such as an extraordinarily small brain
size, may represent the primitive state before positive selection acted on the
trait. The difference is that the state (e.g., a small brain) in our ancestors was
normal at the time, as would have been the pleiotrophic effects of its associ-
ated genes.
48. Falk et al. 2000.
49. González-José et al. 2008.
50. Data from Dmanisi, Republic of Georgia, and from Australopithecus sug-
gest that the trend for enlarging brains had already begun by about 3 million