This commentary focuses on the omission of genetic and environmental variation in several competing evolved motive dispositions that not only react to different environmental contexts but also result in people structuring contexts to obtain psychological rewards. Cross-cultural research is poor evidence for alternate strategies because natural selection may operate to produce geographical variation in dispositional tendencies. Finally, I defend a traditional concept of plasticity in opposition to the alternate strategies concept of flexibility.

The central question facing sleep and dream science today seems to be: What is the physiological basis of the subset of NREM dreams that are qualitatively indistinguishable from REM dreams (“apex dreams”)? Two competing answers have emerged: (1) all apex dreams are generated by REM sleep control mechanisms, albeit sometimes covertly; and (2) all such dreams are generated by forebrain mechanisms, independently of classical pontine sleep-cycle control mechanisms. The principal objection to the first answer is that it lacks evidential support. The principal objection to the second answer (which is articulated in my target article) is that it takes inadequate account of interactions that surely exist between the putative forebrain mechanisms and the well established brainstem mechanisms of conscious state control. My main response to this objection (elaborated below) is that it conflates nonspecific brainstem modulation – which supports consciousness in general – with a specific pontine mechanism that is supposed to generate apex dreaming in particular. The latter mechanism is in fact neither necessary nor sufficient for apex dreaming. The putative forebrain mechanisms, by contrast, are necessary for apex dreaming (although they are nor sufficient, in the limited sense that all conscious states of the forebrain are modulated by the brainstem).

Whereas many researchers see a heuristic potential in the covert REM sleep model for explaining NREM sleep mentation and associated phenomena, many others are unconvinced of its value. At present, there is much circumstantial support for the model, but validation is lacking on many points. Supportive findings from several additional studies are summarized with results from two new studies showing (1) NREM mentation is correlated with duration of prior REM sleep, and (2) REM sleep signs (eye movements, phasic EMG) occur frequently in NREM sleep. The covert REM sleep model represents one class of explanatory models that combines the two assumptions of mind-body isomorphism and a 1-gen mentation generator; its future development will depend largely upon a more detailed understanding of sleep state interactions and their contribution to mind-body isomorphisms.

Preference for partners with low fluctuating asymmetry (FA) may produce “good gene” benefits. However, Gangestad & Simpson's analysis does not exclude immediate benefits of fertility. Low FA is related to fertility in men and women. Short-term changes in FA are correlated with fertility in women. It is not known whether temporal fluctuations in the FA of men are related to short-term fertility status.

One implication of Laland, Odling-Smee & Feldman's niche construction model concerns the significance of the role of behavioural or cultural traits in comparative analysis. In this commentary it is suggested that cladistic methods already recognise this importance, and that behavioural characters may play a key role in hominid speciation and the definition of species.

No doubt all our behavior is the result of evolution, but I express skepticism about the validity of detailed arguments that purport to explain in detail how or why this occurred historically.

We believe that this has been a constructive debate on the topic of memory consolidation and REM sleep. It was a lively and spirited exchange – the essence of science. A number of issues were discussed including: the pedestal technique, stress, and early REMD work in animals; REM windows; the processing of declarative versus procedural memory in REM in humans; a mnemonic function for theta rhythm in waking but not in REM sleep; the lack of cognitive deficits in patients on antidepressant drugs that suppress or eliminate REM sleep; the disposition of conscious (dreams) and nonconscious material of REM sleep; and finally our theory of REM sleep. Although our position was strongly challenged, we still hold that REM sleep serves no role in the processing and consolidation of memory.

Niche construction is a potentially important concept for the human behavioural sciences but we question how it differs from models of gene-culture coevolution and whether it can be developed in the detailed ways that will be necessary if it is going to make a significant contribution to the human behavioural sciences.

Laland et al. rightly observe that the pressures affecting the evolution of a trait include the previous effects the trait has had on the environment. Ignoring this would be like ignoring the effect of compound interest: a distortion, not a simplification. However, cultural evolution is not niche construction. In niche construction one mechanism has effects over multiple paths. Cultural evolution involves the effects of several mechanisms.

The most challenging objections to the Threat Simulation Theory (TST) of the function of dreaming include such issues as whether the competing Random Activation Theory can explain dreaming, whether TST can accommodate the apparently dysfunctional nature of post-traumatic nightmares, whether dreams are too bizarre and disorganized to constitute proper simulations, and whether dream recall is too biased to reveal the true nature of dreams. I show how these and many other objections can be accommodated by TST, and how several lines of new supporting evidence are provided by the commentators. Accordingly TST offers a promising new approach to the function of dreaming, covering a wide range of evidence and theoretically integrating psychological and biological levels of explanation.

Prior to agriculture, human societies were small, with little variation for good genes sexual selection (GGSS) to work on. Across cultures, variation in paternal care makes the benefits of GGSS highly variable. Despite these caveats, female preferences for traits like male body symmetry suggest one reason for female short-term mating is gene shopping.

Cultural evolution may be even more prolific in the generation of new forms than is biological evolution – especially when it takes the form of creative genius. Yet evolutionary theories have tended to overlook the factors that might select for outstanding individual creativity. A recent dual-inheritance theory is outlined and then integrated with the niche-construction theory of Laland et al.

Human behavior can be analyzed using game theory models. Complex games may involve different rules for different players and may allow players to change identity (and therefore, rules) according to complex contingencies. From this perspective, mating behaviors can be viewed as strategic “plays” in a complex “mating game,” with players varying tactics in response to changes in the game's payoff matrix.

I show that there is a link between the evolution of organisms and the evolution of ideas. In particular, if conformity is selected for, then mechanisms are needed so that “mutations” of ideas can occur. Creativity acts as a counter-force to conventional intelligence, so that ideas can develop that do not just elaborate existing paradigms, but oppose these paradigms. Sometimes oppositional ideas go too far, however, and wisdom acts as a force to bring the old and the new together. The dialectic thus integrates intelligence, creativity, and wisdom, with intelligence serving as thesis, creativity as antithesis, and wisdom as synthesis.

Women's mating strategies have typically been characterised as restrictive or coy. However, recent research on sociosexual behaviour suggests that the frequency of women's extra-pair copulations is a function of an unrestricted personality. While agreeing with the general thrust of Gangestad & Simpson's strategic pluralism theory we suggest that it is more likely a matter of finely calculated reproductive opportunism.

The worldwide variation in mating strategies can be explained by differential paternal investment theory, which traces the differences back to the climates where the various peoples (races) evolved. Male provisioning is necessary for women and children to survive cold winters, which is less essential for tropical women. Androstenone may be the substance that makes symmetrical men smell better to fertile females.

The antipathy toward group selection expressed in the target article is puzzling because Laland et al.'s ideas dovetail neatly with modern group selection theory.

Although we find Gangestad & Simpson's argument intriguing, we question some of its underlying assumptions, including: (1) that fluctuating asymmetry (FA) is consistently heritable; (2) that symmetry is driving the effects; (3) that use of parametric tests with FA is appropriate; and (4) that a short-term mating strategy produces more offspring than a long-term strategy.

Inclusion of cultural variables in the study of human evolution is essential but introduces problems of vagueness, nonspecificity, and overgeneralization. Recognition of intracultural variation and conflict, and inclusion of ontogenetic processes such as individual learning are antidotal.

Gangestad & Simpson provide a persuasive argument that both men and women have evolved conditional mating strategies. Their references to “ancestral” males and females are rather vague, which is unfortunate, as they seek to justify their arguments by invoking human evolutionary history. When one actually examines the evidence for human evolution further, more support for their arguments can be found, as predominant types of mating strategies are likely to have shifted in light of environmental and anatomical developments. We can also see in the archaeological record evidence for a further dimension of strategic pluralism – the use of material culture to advertise good genes in some species of ancestral males.