Having two kidneys provides a crucial backup system. While humans can survive with only one functioning kidney, the presence of two offers significant advantages.
Redundancy and Reserve Capacity
The most prominent reason for having two kidneys is redundancy. This built-in backup ensures continued kidney function even if one kidney is damaged or fails. As noted in several sources (La Trobe University, eMedicineHealth), a single kidney can handle the body's filtration needs. However, having two provides a substantial reserve capacity. This is especially important in cases of kidney injury or disease, where one kidney can compensate for the other's reduced function. The extra kidney mass acts as insurance against potential kidney failure ([reference citing 30% function needed for survival]).
Evolutionary Advantages
The evolutionary benefit of having two kidneys is likely tied to survival. In early humans, kidney damage from injury or infection could have been a frequent cause of death. The presence of two kidneys significantly increased the odds of survival in such scenarios. While this remains a theory, the redundancy offered by two kidneys is a strong selective advantage. As explained on Reddit (r/explainlikeimfive), the evolutionary history points to a significant benefit associated with possessing a paired organ.
Efficient Waste Removal and Blood Filtration
Although a single kidney can manage the body's filtration needs, having two enhances the efficiency of waste removal and blood filtration. Two kidneys can process blood more rapidly and effectively than one, ensuring optimal maintenance of fluid and electrolyte balance. This increased capacity becomes especially beneficial during periods of increased metabolic stress or illness. Resources like the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) highlight the vital role kidneys play in blood filtering.
Summary
In conclusion, the existence of two kidneys is primarily due to the evolutionary advantage of redundancy and the increased efficiency of waste removal and blood filtration. While one kidney is sufficient for survival, having two provides a robust and reliable system for maintaining overall health.
