Grok’s answer to this question:

Post-neo-Darwinism is not a single, formal scientific theory with a precise definition. It is a loose label used in different contexts for evolutionary ideas that extend, refine, or critique the neo-Darwinian modern synthesis.

Neo-Darwinism (the baseline)

Neo-Darwinism generally refers to the modern evolutionary synthesis (roughly 1918–1940s and its later refinements). It integrates Darwin’s natural selection with Mendelian genetics and population genetics. Key features include:

• A strongly gene-centric view of evolution.
• Random genetic mutation as the primary source of variation.
• Natural selection as the main creative force shaping adaptations.
• Gradual change via shifts in allele frequencies.
• Rejection of the inheritance of acquired characteristics (Weismann barrier).

Later popularizations (e.g., Hamilton’s inclusive fitness and Dawkins’ “selfish gene”) further emphasized adaptationism and gene-level selection.

What “post-neo-Darwinism” points to

The term appears in a few overlapping senses:

• In some usages (e.g., certain European discussions), it simply names the later 20th-century mainstream that combines the modern synthesis with gene-centrism and broad adaptationism. In this framing, newer approaches such as evolutionary developmental biology (evo-devo) are sometimes presented as potentially moving beyond it.
• More commonly in critical or progressive literature, it labels efforts to go beyond a strict neo-Darwinian picture by incorporating additional mechanisms and a more pluralistic view of causation. Related ideas include the Extended Evolutionary Synthesis (EES), calls for a “postmodern synthesis,” and the “Third Way of Evolution.” These emphasize:
  • Transgenerational epigenetic inheritance and other non-genetic forms of inheritance.
  • Niche construction (organisms actively modify their environments).
  • Developmental bias, phenotypic plasticity, and evo-devo processes.
  • Multilevel selection.
  • Horizontal gene transfer, endosymbiosis/symbiogenesis, and mobile genetic elements.
  • Complex regulatory networks rather than simple “one gene–one trait” mapping.
  • In some versions (e.g., work associated with James Shapiro or Denis Noble), greater organismal or cellular agency in generating variation (“natural genetic engineering”).

Genomic and systems-biology perspectives (e.g., Eugene Koonin) have also stressed that neutral processes, purifying selection, gene duplication, HGT, and other non-adaptive or non-gradual mechanisms play major roles, so natural selection of beneficial mutations is important but not all-embracing.

Historical note

In 1986, population geneticist Joseph Felsenstein published a skeptical review titled “Waiting for Post-Neo-Darwin.” He noted that popular claims of a revolutionary replacement for the modern synthesis often consisted of buzzwords (developmental constraints, punctuated equilibrium, epigenetics, etc.) that did not yet form a coherent alternative theory. Many of those themes have since been productively integrated into evolutionary biology without overturning its core framework.

Bottom line

Post-neo-Darwinism is best understood as a descriptive umbrella for more pluralistic, post-genomic, and systems-oriented views of evolution. These views retain natural selection and genetic inheritance as central while giving greater weight to development, non-genetic inheritance, horizontal processes, niche construction, and the complexity of genotype–phenotype mapping. Mainstream evolutionary biology has absorbed many of these insights; whether they require a formal “new synthesis” or simply an expanded modern synthesis remains debated.

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I also asked my browser’s AI. Here’s it’s answer:

Post-neo-darwinism refers to a set of modern evolutionary theories that challenge or extend the Modern Synthesis (traditional neo-Darwinism) by incorporating mechanisms beyond random genetic mutation and natural selection.  It encompasses frameworks such as the Extended Evolutionary Synthesis (EES), post-darwinism, and integrative synthesis, which emphasize the roles of developmental plasticity, epigenetics, niche construction, and symbiosis in evolutionary change. 

Key distinctions from traditional neo-Darwinism include:

• Mechanisms of Variation: Unlike neo-Darwinism, which views variation as primarily random and genetic, post-neo-darwinist theories suggest the environment can influence variation through epigenetic modifications and developmental plasticity, sometimes allowing for inheritable changes not solely dictated by DNA sequence alterations. 
• Role of the Organism: These theories shift the view of the organism from a passive vehicle for gene replication to an active agent in evolution through niche construction and behavioral choices, arguing that symbiosis and coherence are as fundamental as competition.
• Conceptual Frameworks: Proponents argue for a multilevel and systems-based understanding of biology, where gene function is context-dependent and cellular cognition plays a central role, rather than relying on a strict “gene-centric” or “selfish gene” narrative. 
• Integration of New Data: The framework integrates findings from genomics, evo-devo, and prokaryotic biology, suggesting that the traditional “modern synthesis” is incomplete because it fails to account for complex gene networks, pleiotropy, and non-genetic inheritance.