The easiest possible game changer by far would should be the discovery of black powder. There are several threads dealing with this idea however so lets look at PODs for public health improvements.
1. Scurvy Treatment
The easiest way to achieve this would probably be to make Sauerkraut a staple diet like Kimchi is in Korea.
2.
Vaccination/Inoculation
Yep, pretty much doable at any time.
3. Germ theory
Maybe the invention of a simple microscope might help. Both, a water drop or glass beat microscope should be doable fairly early. Convincing people that germs a thread might be (slightly) easier if they can be seen.
http://bizarrelabs.com/micro.htm
http://micro.sci-toys.com/waterdrop
4. Xylem/Wood Water Filter
If you want to go really early there might be a path to an ice age water filter.
“Birch bark tar has been used in northern Europe as a superior mastic as far back as 80,000 years. It was found on a Neanderthal spear point, with a thumb print. Pieces of chewed birch bark tar with human teeth marks go back as far as 11,000 year...” It was manufactured to build stuff, but also had some health benefit.
http://www.primitiveways.com/birch_bark_tar.html
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Producing safer drinking water using plant xylem April 8, 2014 / Sarah Shailes
The World Health Organisation (WHO) estimates that 1.6 million people die each year from rom gastrointestinal diseases caused by a lack of clean water (1). The biggest threats from unclean water are infectious diseases caused by bacteria (e.g. cholera), viruses (e.g. hepatitis), protozoa (e.g. giardiasis) or parasites (e.g.schistosomiasis). In developed countries we often take clean water for granted, relying on various technologies including chlorination, boiling, pasteurisation, UV-disinfection or filtration to make our water safe. However, in less developed countries, especially in small rural communities, these technologies are often too expensive or impractical. In a paper published recently in PLOS ONE, the authors explore the use of plant xylem vessels, which are found in the stems of plants, as inexpensive water filters.
Xylem vessels are tubes that carry water (and some nutrients) from the roots of plants to the stems. The vessels themselves are made up of cells that die as they mature leaving a strengthened cell wall with pores called pits in their sides . Groups of parallel vessels are arranged together so that water flows between the parallel tubes through the pits . The size of the pits of xylem vessels vary from a few nanometers to hundreds of nanometers, just the right kind of size to potentially filter out disease-causing microbes. Flow of water through xylem vessels of conifers (gymnosperms) and flowering plants (angiosperms).
The xylem vessal cells of conifers are smaller in diameter and shorter than those of flowering plants. Although this makes them less efficient at transporting sap, it also makes conifer stems more ideal for filtration because the water is forced to pass through the pits more often (more filter points) so a shorter length of stem is needed. Also, xylem vessels make up a greater cross-section of a conifer stem, which is useful for a filter material. The authors tested the filtering capability of short lengths of pine stem. They found that several litres of water could flow through 3 cm3 of pine stem per day . This is enough to meet the clean drinking water needs of one person.
The xylem filters were efficient at filtering out bacteria. The pits in the xylem of the pine stem are too large to filter out viruses from the water but it is possible that stems from other plant species with smaller xylem pits, such as deciduous trees might be more suitable for this. Since all that is required to make the filter is a tube, a suitably sized plant stem, and a way of sealing the connection, xylem water filters could be cheaply made and maintained by individuals. Therefore, plant stems have the potential to be used as inexpensive, small-scale water filters.”
Have some shaman come up with the idea that trees healing properties might be easier to harvest by filtering water trough them and additionally clean up muddy, bad tasting water. Bahm, stone age health revolution ;-).
i just want to get ideas, basically