Thyroid rhythm phenotypes and hominid evolution: a new paradigm implicates pulsatile hormone secretion in speciation...

Area of Science:

• Evolutionary biology
• Endocrinology
• Human origins

Background:

• Thyroid hormones (THs) are crucial regulators of vertebrate development, reproduction, and stress responses.
• THs exhibit pulsatile secretion, forming species-specific rhythms with developmental shifts.
• Individual variations in TH rhythms (TR phenotypes) correlate with variations in morphology, reproduction, and behavior.

Purpose of the Study:

• To present a novel theory on the role of thyroid hormones in vertebrate evolution.
• To discuss how this theory explains evolutionary changes in hominid morphology, behavior, and life history.

Main Methods:

• Review of existing literature and theoretical concepts.
• Application of the novel theory to explain specific hominid evolutionary phenomena.

Main Results:

• The theory posits that selection on TR phenotypes drives coordinated evolutionary changes across multiple traits.
• It offers explanations for convergent bipedalism, sexual dimorphism, and coordinated morphological/neurological changes in hominids.
• The framework accounts for adaptations like cold tolerance in Homo neanderthalensis and regional variations in hominid populations.

Conclusions:

• This thyroid hormone rhythm-based theory provides a unifying framework for understanding human origins and evolution.
• It highlights the interconnectedness of traits under thyroid control and their rapid, coordinated evolutionary trajectory.
• The paradigm has significant implications for understanding human health and evolutionary adaptations.