AKA Harris' lines or growth arrest lines, these are lines that appear in bones due to temporary retardation of bone growth.

They are dense lines parallel to the growth plates in the long bones (in other words, horizontal lines across the bone). They occure most often in the bones of the leg, particularly the distal tibia. They originally form at the epiphyses, but they remain as the as the bone continues to grow past them.

Harris lines are caused by poor nutrition (starvation or malnutrition) and some types of sickness. Because of this, they are of interest to archeologists studying ancient populations. While there may be no way to tell exactly what caused the lines, by looking at them you can see how often an individual underwent severe streeses of this sort*, and how severe the stress was. You can also get some idea as to how old the individual was when the line was formed by looking at where it appears on the bone. Regular occurrences of Harris lines may be an indication of seasonal stresses, which may imply that food was short at certain times of the year.

Harris lines are usually seen by x-ray. Other indicators of restricted growth are enamel hypoplasia of the teeth (which is visible to the naked eye) and Wilson lines (also on the teeth, but not visible to the eye). These markers require more severe stress to be produced than do Harris lines.

Harris lines were named after Henry Albert Harris, a Welsh anatomist, 1886-1968.

* There is some reason to doubt that Harris lines are always good recorders of the number of times an individual underwent severe stress. It is accepted that hunter and gatherer populations were, on average, healthier and better nourished than early agriculturalists. But at the same time, hunter and gatherers tend to have more Harris lines (while at the same time having fewer Wilson lines). This could be because bone repairs itself over time, which might erase Harris lines (teeth are much less likely to repair themselves; the Wilson lines may also form earlier in childhood). Another aspect to take into consideration is that Harris lines are the result of growth being slowed or stopped for a time, and then resuming. If growth is slowed over a very long time, Harris lines may not be in evidence (that is, Harris lines show sharp changes in bone growth. If bone growth is always slow, then Harris lines may not form. In a well nourished and healthy individual a dip in health will be recorded, but in an individual who is always undernourished, there may not be any Harris lines).

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