@article{oai:air.repo.nii.ac.jp:00002791,
 author = {新山, 喜嗣 and NIIYAMA, Yoshitsugu},
 issue = {2},
 journal = {秋田大学大学院医学系研究科保健学専攻紀要},
 month = {Oct},
 note = {地球上に生命が誕生してから37億年になるが, 実のところその半分以上を占める20億年の間は生物の死は絶対的な
ものではなかった. 生物に寿命としての絶対的な死が伴うようになったのは, 生物が原核生物から真核生物に進化し
てからのこの17億年間のことである. この絶対的な死をもたらす要因の一つに, ヘイフリック限界の名で呼ばれる細
胞分裂の回数制限がある. さらに, 生物は加齢に伴って生存に不適切な細胞が増えるが, そのような細胞はアポトー
シスと呼ばれるメカニズムによって秩序正しく除去される. このように, 生物には身体の内部に積極的に死をもたら
す仕組みがあるが, 一定の期間を越えて個体が生存しないことが種の存続という点では有利であることから, そのよ
うな生物種のみが現在まで地球上に残っているのかもしれない. しかし, 将来には予想外の科学技術の進歩によって,
生存期間に制限がない生物種が存在しても種の存続に不都合が生じない可能性がある. もっとも, 現代の宇宙物理学
が示すところでは, 生物の身体を構成する原子が宇宙に存在できるのも永遠ではない. このことからすれば, 自然科
学の中で生命を捉える限り, ｢永遠の生命｣はあくまで相対的なものとなる., About 3,700 million years have passed since life was first born on the earth. However, for its first
2,000 million years, more than half of this time, death was not yet absolutely bound to occur. It is only
after eukaryotic creatures evolved from prokaryotes that organisms started to experience death as an
absolute limit to their lifespan. In other words, mortality has existed for only the last 1,700 million years.
The first factor that brings the absolute death is the Hayflick limit, the mechanism that restricts the
number of times a cell can continue to divide before they can no longer. The second factor is the
mechanism allowing for cell  suicide , apoptosis. With age, nonfunctional or harm cells in a creature can
increase, but these defective cells are removed in good order through programmed cell death. In this way,
there is a physical mechanism inside the body to bring death positively, so that the creature does not
survive longer than a certain period of time. It can be said that the only creatures currently remaining on
the earth are those creatures with these death-involving mechanisms. However, through possible future
advances in science and technology, even perhaps preventing death altogether, the species might be able to
survive forever. Yet, present-day astrophysics has shown that even the very atoms that compose our
bodies are not eternal. Knowing this, the idea of everlasting life becomes relative, as far as we understand
life in the natural sciences.},
 pages = {1--13},
 title = {ヒトにとって死は不可避なのか(その１) ―バイオロジーからの検討―},
 volume = {24},
 year = {2016}
}