Human Infants Initially Possess Over 300 Bones, Later Fuse and Disappear over Time - A Mystery lies in Their vanishing
How Many Bones Does a Human Baby Have?
In contrast to many baby mammals that are walking shortly after birth, human infants heavily rely on adults for several years due to their inability to perform numerous tasks. However, there's one area where babies outperform adults - the number of bones. Surprisingly, a newborn baby has around 275 to 300 bones, significantly more than the typical 206 bones in an adult's body.
The surplus of bones in babies serves a specific purpose: to facilitate a successful birth. A human infant's large size necessitates the ability to fit through a relatively small opening. This need for flexibility results in babies having a larger number of smaller bones, many of which are made of flexible cartilage instead of mature bone tissue.
One of the most noticeable examples of this phenomenon is the soft spot, or fontanelle, at the top of a baby's head. The fontanelle is a space between the five major skull bones, which allows the skull to mold during delivery. As the baby grows, this space gradually closes, and the skull solidifies.
During childhood, the remaining cartilage gradually changes into bone through a process called ossification. Many of the short bones also fuse into their eventual adult forms. This process, known as osteogenesis, initiates during the eighth week of embryonic development and continues through adolescence.
Ossification follows two main pathways: intramembranous ossification, which forms some of the flat bones of the skull and other irregular bones, and endochondral ossification, which forms the majority of the bones in the skeleton. Intramembranous ossification involves the direct differentiation of mesenchymal cells into bone matrix, while endochondral ossification involves bone tissue growing on top of cartilage "scaffolds" before the cartilage dissolves, leaving just bone behind.
Both intramembranous and endochondral ossification require osteoblasts, cells responsible for producing the bone matrix. This matrix consists of proteins like collagen and minerals like calcium, emphasizing the importance of calcium-rich foods in one's diet.
As children grow, their bones must grow as well. While their newborn cartilage is being replaced with regular bone, a similar process to endochondral ossification ensures that the long bones, such as the femur, can extend in length. Because kids' bones are still developing in this way, they tend to heal from fractures more quickly than adult bones with less risk of lasting damage.
While having an incomplete skull and rubbery bones might initially seem risky from an evolutionary perspective, it's a necessary trade-off to accommodate being upright, bipedal, and having a large brain. The significant energy demands of growing a baby make a pregnancy term of more than 40 weeks unsustainable, and the need to deliver an oversized head through a small opening necessitates the postponement of much of human development until after birth.
An understanding of ossification has been essential in deciphering the evolutionary development of the human skeleton, from its significant number of bones at birth to the eventual decrease to 206 bones in adulthood.
- The excess bones in babies facilitate a successful birth, making it possible for infants to pass through a small opening, which is essential given their large size during delivery.
- The fontanelle, a space between a baby's skull bones, is an example of this flexibility, allowing the skull to mold during delivery.
- Ossification, the process by which cartilage in babies transforms into bone, occurs through two main pathways: intramembranous and endochondral ossification.
- Diet plays a crucial role in the process of ossification, as it involves the presence of proteins like collagen and minerals like calcium, highlighting the importance of calcium-rich foods for a balanced diet.
