Book Three of the Trilogy
Ageing
The New Science of How We Age, Across Every Phenotype
The standard clinical tool for grading skin ageing measures wrinkles. For most of the world’s skin, wrinkles are not the signal. Different is not absent.
Inside the book
The Glogau photoageing classification, introduced in 1994, remains the standard clinical tool for grading how badly skin has aged. It grades almost entirely on wrinkles, fine lines, elastosis, solar lentigines and visible blood vessels, the features characteristic of chronically sun-exposed, lightly-pigmented skin. Applied to a Black woman in her sixties with minimal wrinkling but substantial pigmentary and textural change, the scale reports her as barely aged, because it was never built to see the ageing she is actually experiencing.
The book grounds its argument in the twelve hallmarks of ageing, the framework set out in a landmark 2013 Cell paper and expanded in 2023. Every one operates in skin, scalp and hair follicle alike. What differs sharply is which subset of drivers dominates the visible output in a given tissue and a given phenotype.
Its original contribution is the Pigmentary Paradox, the direct successor to the Inflammation Paradox: the same biological features that delay wrinkling in melanin-rich skin also drive its pigmentary ageing. Senescent fibroblasts lose their output of SDF1, releasing melanocytes from a normal restraint; a higher melanocyte density is also a larger population primed to over-respond to inflammation.
Post-inflammatory hyperpigmentation, in this framework, is not a cosmetic nuisance sitting outside the biology of ageing. It is a compressed, localised version of the same ageing mechanism playing out over months instead of decades.
The evidence
'Black don't crack' captures a partial truth, and then flattens it into a myth. Skin ages on a different schedule, through different visible signs. Different is not absent.
African-descent skin shows minimal wrinkling and well-preserved dermal firmness into the fifties, alongside a burden of scalp and follicular ageing that is frequently the more serious ageing story even though it rarely shows on the face.
A 2023 Nature finding reframes greying: melanocyte stem cells at the follicular bulge become stuck rather than exhausted, making it a reversible dormancy rather than simple cell loss.
Core themes
Skin ageing · Melanin and ageing · Pigmentation versus wrinkles · Twelve hallmarks of ageing · Scalp and hair ageing · Menopause · Microbiome ageing · Future anti-ageing science