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History of tuberculosis

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History of tuberculosis
Cristóbal Rojas · Public domain

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Through Neolithic, Bacteria and Antibiotic

Tuberculosis is an infectious disease caused by bacteria of the Mycobacterium tuberculosis complex (MTBC). Throughout history, tuberculosis has been known by differing names, including consumption, phthisis, and the White Plague. Paleopathological evidence finds tuberculosis in humans since at least the Neolithic (approximately 10,000-11,000 years ago), with molecular studies suggesting a much earlier emergence and co-evolution with humans.

Phylogenetic analyses indicate that the TB originated in Africa and evolved alongside human populations for tens of thousands of years. The disease spread globally through human migrations, adapting to different human populations and eventually developing into several distinct lineages with varying geographic distributions. While TB has affected humanity for millennia, it became particularly prevalent during industrialization when urban overcrowding aided transmission. The medical understanding of tuberculosis transformed in the 19th century with Robert Koch's 1882 identification of Mycobacterium tuberculosis as the causative bacterium, followed by the development of vaccines and antibiotic treatments in the mid-20th century.

Origins

The modern understanding of the evolutionary origins of Mycobacterium tuberculosis has been revolutionized by recent genomic and phylogenetic research. Current evidence suggests that tuberculosis is an ancient human disease that co-evolved with human populations for tens of thousands of years, rather than a recent acquisition from domesticated animals during the Neolithic as previously believed. There has also been a claim of evidence of lesions characteristic of tuberculosis in a 500,000-year-old Homo erectus fossil, although this finding is controversial.

Phylogenetic evidence

Comprehensive phylogenetic analyses of the Mycobacterium tuberculosis complex (MTBC) demonstrate an African origin for the pathogen. Whole-genome sequencing of modern TB strains reveals that the bacteria emerged in Africa and followed human migration out of Africa. Research analyzing 259 global TB clinical strains suggests that tuberculosis arose roughly 70,000 years ago, expanding in two major waves: first around 67,000 years ago during human migration to South Asia, and again around 46,000 years ago during migrations to the Near East, Europe, and Asia.

Within TB, researchers have identified multiple lineages (currently nine human-adapted lineages) associated with different geographical regions. These include Lineage 1 (East Africa, Philippines), Lineages 2–4 (Eurasia), Lineages 5–6 (West Africa), Lineage 7 (Ethiopia), Lineage 8 (East Africa), and Lineage 9 (East Africa). Animal-adapted lineages, including M. bovis which infects cattle, evolved from human strains rather than the reverse, contradicting earlier theories about TB's origins.

The discovery of M. tuberculosis Lineage 8 strains in East Africa, which retain genetic features seen in more ancestral mycobacteria but absent in other TB lineages, provides evidence for the ancient African origin of tuberculosis.

Paleopathological evidence

The oldest confirmed paleopathological evidence of human tuberculosis dates to the Pre-Pottery Neolithic (10,000–11,000 years ago) in the Near East. Key early cases include remains from Dja'de el Mughara and Tell Aswad in Syria (8800–7600 BCE), Ain Ghazal in Jordan (7250 BCE), and Atlit Yam in Israel (6200–5500 BCE), where molecular analyses confirmed the presence of TB DNA. In Europe, the earliest confirmed cases come from the Early Neolithic Linear Pottery culture sites in Germany (5400–4800 BCE).

A controversial finding reported in 2014 based on DNA from 1,000-year-old skeletons in Peru suggested that tuberculosis might have been transmitted to humans from seals, possibly originating only 6,000 years ago. However, subsequent research has challenged this interpretation. The Peruvian samples showed evidence of a TB strain related to M. pinnipedii (seal TB), but this represents a localized zoonotic transfer specific to pre-colonial South America rather than the origin of human tuberculosis. These seal-derived strains infected coastal populations and spread inland but were eventually replaced by European strains of M. tuberculosis brought in by colonists. This finding represents an example of animal-to-human transmission, but does not contradict the evidence for much earlier human tuberculosis in Africa and Eurasia.

The limited paleopathological evidence from the Upper Paleolithic (40,000–10,000 years ago) despite its importance in TB evolution represents a paradox.This may be explained by the low population density of Paleolithic hunter-gatherers, which would have limited TB transmission and skeletal signs, or by limitations in identifying ancient tuberculosis.

Early evolution

Genomic research indicate that the emergence and spread of tuberculosis were not linked to animal domestication during the Neolithic, but rather to human population dynamics. The Neolithic demographic transition (with increased population density and sedentism) aided tuberculosis transmission and allowed it to become more widespread, but long before this, the pathogen had already become adapted to humans.

The co-evolution between TB and humans is evidenced by the adaptation of different tuberculosis lineages to different human populations, reflecting geographical patterns of human migration and settlement. Genetic studies also show evidence of selection pressure exerted by tuberculosis on human populations, such as the changing frequency of TB susceptibility variants like TYK2 P1104A in Europeans over the past 2,000 years.

Although relatively little is known about its frequency before the 19th century, its incidence is thought to have peaked between the end of the 18th century and the end of the 19th century. Over time, the various cultures of the world gave the illness different names: phthisis (Greek), consumptio (Latin), yaksma (India), and chaky oncay (Incan), each of which make reference to the "drying" or "consuming" effect of the illness, cachexia.

In the 19th century, TB's high mortality rate among young and middle-aged adults and the surge of Romanticism, which stressed feeling over reason, caused many to refer to the disease as the "romantic disease".

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