An Adaptive Threshold in Mammalian Neocortical Evolution (original) (raw)
Figure 3
Ln-transformed plots showing GI values as a function of adult brain weight (A, B), neocortical volume (C), and cortical neuron number (D).
(A) Regression analysis using one non-linear fit for all values (101 species [see Table S1, with C. volans being omitted from this analysis], y = 0.018_x_2+0.037_x_+0.014, R2 = 0.612, p = 6×10−5); (B–D) regression analyses using two different linear functions (B, 101 species, blue line: y = 0.075_x_−0.481, R2 = 0.56, p = 4×10−5, red line: y = 0.245_x_+0.018, R2 = 0.73, p = 1×10−5; (C), 32 species (see Table S1, column E), blue line: y = 0.050_x_−0.194, R2 = 0.21, p = 0.017, red line: y = 0.154_x_−1.09, R2 = 0.82, p = 0.004; (D), 25 species (see Table S8), blue line: y = 0.072_x_−1.188, R2 = 0.81, p = 1×10−4; red line: y = 0.140_x_−2.370, R2 = 0.98, p = 3×10−5) for species with GI values of <1.5 (blue triangles) and >1.5 (red circles), respectively; mouse and human (when depicted) are indicated by green symbols. The inset in (B) shows the Akaike Information Criterion (AIC) values for models fitted with one to five linear slopes; note that a two-slope model best explains the data.