We know that life expectancy has increased over the last 200 years. An average man born in 1800 had a life expectancy of 35 years. In 1900, he would have made to 47 and by 1950, average life expectancy was up to 68 years. Today it's up to about 78.
1. Cancer-causing nuclear mutations/epimutations
These are changes to the nuclear DNA (nDNA), the molecule that contains our genetic information, or to proteins which bind to the nDNA. Certain mutations can lead to cancer, and, according to de Grey, non-cancerous mutations and epimutations do not contribute to aging within a normal lifespan, so cancer is the only endpoint of these types of damage that must be addressed.
2. Mitochondrial mutations
Mitochondria are components in our cells that are important for energy production. They contain their own genetic material, and mutations to their DNA can affect a cell’s ability to function properly. Indirectly, these mutations may accelerate many aspects of aging.
3. Intracellular aggregates
Our cells are constantly breaking down proteins and other molecules that are no longer useful or which can be harmful. Those molecules which can’t be digested simply accumulate as junk inside our cells. Atherosclerosis, macular degeneration and all kinds of neurodegenerative diseases (such as Alzheimer's disease) are associated with this problem.
4. Extracellular aggregates
Harmful junk protein can also accumulate outside of our cells. The amyloid senile plaque seen in the brains of Alzheimer’s patients is one example.
5. Cell loss
Some of the cells in our bodies cannot be replaced, or can only be replaced very slowly - more slowly than they die. This decrease in cell number causes the heart to become weaker with age, and it also causes Parkinson's disease and impairs the immune system.
6. Cell senescence
This is a phenomenon where the cells are no longer able to divide, but also do not die and let others divide. They may also do other things that they’re not supposed to, like secreting proteins that could be harmful. Immune senescence and type 2 diabetes are caused by this
7. Extracellular crosslinks
Cells are held together by special linking proteins. When too many cross-links form between cells in a tissue, the tissue can lose its elasticity and cause problems includingarteriosclerosis and presbyopia.
1 In 1986, he co-founded Man-Made Minions Ltd to pursue the development of an automated formal program verifier.