Lumbar Lordosis

Healthy adult humans have an anterior (forward) curvature of the lower (lumbar) vertebral column known as lumbar (or lumbosacral) "lordosis."  A lordosis is any anterior-ward convexity in the vertebral column, and the normal adult vertebral column has two of them - one in the lumbar region and one in the cervical region (an anterior-ward concavity is known as a kyphosis, and in humans there are two of these as well - one in the thoracic region and one in the sacrum).  This lordosis is believed to be functionally important o bipedal locomotion, in that it serves to move the center of the trunk posteriorly and thus over the hip joints (reducing the amount of muscular effort required to balance body weight over the lower limbs in bipedal standing and walking).  Lumbar lordosis is  not found in great apes, likely because of their lack of habitual erect posture, and the extreme reduction in the length of the lumbar region in the great apes.  It has conventionally been thought that lordosis develops in human children during the first year of life, in response to new biomechanical loads (which influence the growth of the vertebrae) as they begin to pull themselves up into standing postures prior to taking their first steps.  However, recent research suggests that lordosis is evident in the lumbosacral region of as much as 60% of human fetuses, suggesting that there may be a genetic component to the morphology.