Forager and farmer evolutionary adaptations to malaria evidenced by 7000 years of thalassemia in Southeast Asia

Thalassemias are inherited blood disorders that are found in high prevalences in the Mediterranean, Southeast Asia and the Pacific. These diseases provide varying levels of resistance to malaria and are proposed to have emerged as an adaptive response to malaria in these regions. The transition to agriculture in the Holocene has been suggested to have influenced the selection for thalassemia in the Mediterranean as land clearance for farming encouraged interaction between Anopheles mosquitos, the vectors for malaria, and human groups. Here we document macroscopic and microscopic skeletal evidence for the presence of thalassemia in both hunter-gatherer (Con Co Ngua) and early agricultural (Man Bac) populations in northern Vietnam. Firstly, our findings demonstrate that thalassemia emerged prior to the transition to agriculture in Mainland Southeast Asia, from at least the early seventh millennium BP, contradicting a long-held assumption that agriculture was the main driver for an increase in malaria in Southeast Asia. Secondly, we describe evidence for significant malarial burden in the region during early agriculture. We argue that the introduction of farming into the region was not the initial driver of the selection for thalassemia, as it may have been in other regions of the world.

Seed production.

Seeds are effective and efficient plant reproductive and dispersal structures consisting of an embryo, food supply and protected covering. As the start of the next generation, seeds occupy a critical position in plant life history and in the survival of the species (Black et al., 2000). Seed husbandry formed the basis for early agriculture and eventual civilization. People learned to plant, harvest, and preserve the seeds of certain grasses for winter and they abandoned nomadic life to build permanent settlements (Copeland and McDonald, 2001). Long viability has allowed seeds to be passed from generation to generation, with some, e.g. the Indian lotus (Nelumbo nucifera) remaining viable for as long as 1000 years (Janick, 1986). Seeds are remarkably varied and diverse. The orchid species boasts the smallest known seed, a dust-like particle hardly visible to the naked eye (Copeland and McDonald, 2001). Large perennial plants typically have the heaviest seed size, e.g. coconut.. Shape ranges from round or oval in many seed species, to triangular, elliptic, elongated, spiked, thorned, and hairy or winged, depending on the natural method of disposal. Together with differences in size and shape, seeds are highly diverse in a number of other aspects, many of which are relevant to horticultural production and seed technology which has developed to address such issues as seed dormancy, viability and storage life.

Crop protection.

Crop protection procedures have existed since the first attempts at early agriculture. While cultivation of a vast range of crops is vital our existence, these same plants are highly attractive to a diverse range of invertebrate and vertebrate pests, and disease pathogens. Competition from weed species also occurs on a worldwide scale. Even with the many forms of crop protection practised today, losses due to pests and diseases range from 10 to 90%, with an average of 35-40% for all potential food and fibre crops (Peshin, 2002).