the long line of our ancestry Why do we celebrate New Year Day? Why do we make those new-year- resolu- tions? A year is such a short period of time, at least when you are of age which recognizes the age significance. Maybe you have a somewhat more pleasant score, but one year is only 1.3% of my age. Even if you accomplish your yearly resolution(s), what are substantial changes in your life? Not to mention changes in the existence of your species, that is us, humans? Nowadays you can trace your mitochondrial ancestry, your ‘African Eve’, the mother of all mothers who lived in Africa some 170 thousand years ago. And, if you consider your African mitochondrial ancestry to be a unit of time, let’s call it ‘African mitochondrial year’, it follows that one our calendar year is no more than 3 minutes of that year.
Then you learn that you are, factually, a ‘third chimpanzee’ who some four million years ago suffered mutations the other two relatives were spared of. Take four million years as the ‘third chimpanzee year’ - thereupon one our calendar year is only 8 seconds of that year.
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Then you learn that all multicellular beings, all plants, animals, algae, and fungi, evolved in the last 600 million years through eukaryotic cell for which not only nucleus but mitochondria also are essential. Call it the ‘mitochondrial year’ - one our calendar year is only 54 milliseconds of that year. Further you learn that mitochondria have a bacte- rial ancestry and live within our cells as symbionts (organisms that share a mutually beneficial asso- ciation with other organisms). Mitochondria are organelles in the cell dedicated to energy produc- tion; they were once bacteria, and in appearance they still look like bacteria. The number of mito- chondria in the cells of our bodies depends on the metabolic demand of that particular cell. Metabo- lically active cells, such as those of the liver, kidneys, muscles, and brain, have hundreds or thousands of mitochondria, making up some 40% of the cytoplasm. All in all there are about 10 million billion mitochondria in an adult human, which together constitute about 10% of our body weight. So, one tenth of our body carries typical bacterial genes which regulate the very essence of life - energy production. Enough to claim our bacterial ancestry, but even if we don’t do so, if we don’t go beyond eukaryotic cell, let’s be aware that bacteria were present beyond for a couple of billion years. Present alone! And now living within us and around us, all the time. If life on Earth would got stuck at the bacterial stage for another billion years, you won’t be reading these lines. And when we search for extraterrestrial life, what are chances that life there isn’t stuck at the bacterial stage? |
Schematic illustration of a bacterial cell (a) compared with a eukaryotic cell (b). The illustrations are not drawn to scale; bacteria are about the same size as the mitochondria in (b). |
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