Why drink beer post of the week

In the "good old days", Beer was safer than water to drink.

but now Archeoblog links to a paper saying that Nubian beer contained an antibiotic

they found elevated levels of tetrcyclines in bone from Sudanese Nubia and hypothesized that it was coming from the beer they drank and was present in quantities that strongly suggested that they were purposefully brewing it for that very reason. Not only that, but it was in high enough concentrations to have measurable health effects.