The pluripotent condition may thus be viewed as a transcription factor battlefield in which Oct4, Sox2, and Nanog are dominant and continuously suppress functional expression and activity of lineage specification factors (Niwa, 2007; Smith, 2005) Crucially, however, Oct4 and Sox2 also provide for developmental extinction of pluripotency by directing expression of FGF4.
Several types of response to this rapid climatic change have been proposed for vertebrates, including range shifts to track resource changes, local adaptation to new resources, local extinctions, and developmental plasticity [ 5, 6].
We analyzed among-strain variation in extinction, successful transfer frequencies, developmental delay, and mortality for the nematodes evolved at N = 1.
These fundamental processes were, like the insights gained from the disciplines of evolutionary developmental biology ("Evo-Devo") and geology (mass extinctions), integrated into the "Expanded Synthesis" published in 2004 [ 54, 74].
Sagvolden and colleagues' dynamic developmental theory [ 5], for instance, predicts slower extinction in individuals with ADHD; Tripp and Wickens' dopamine transfer deficit theory [ 4] makes the opposite prediction.
The dynamic developmental theory of ADHD proposes that reinforcement and extinction processes are inefficient because of hypofunctioning dopamine systems, resulting in a narrower time window for associating antecedent stimuli and behaviour with its consequences.
Many of the other findings could equally well support a plasticity interpretation, for example that birds that experienced greater developmental telomere attrition were quick to give up in extinction or when facing increasing costs to obtain reward.
ADHD-related variability may be caused by inefficient behavioural selection mechanisms linked to reinforcement and extinction, as suggested by the recently published dynamic developmental theory (DDT) of ADHD.
A recent comprehensive theory of ADHD, the dynamic developmental theory (DDT), suggests two processes, altered reinforcement processes and inefficient extinction, as being causative of several of the behavioural symptoms in ADHD [ 2, 3].
Taken together, these results suggest that there are developmental differences in the amount of associative change that occurs to CSs during extinction training.
The existence of other, less easily discernible biological traits that might have contributed to the extinction of the Neanderthals – such as differences in reproductive rates or developmental histories – cannot be ruled out, but are not supported by current data.
