death of one or both, mutual benefit was the result. The consumed ceased being a free-living entity and was permanently annexed into the guts of what would grow to become the third domain of life, the one that you are in.
This idea was first presented by the American biologist Lynn Margulis in 1966. It caused rousing controversy and was largely rejected, and she was considered to be heretical. With time, experiments, and evidence, her views were vindicated and are now the orthodoxy. The evidence comes in a number of forms, most simply that complex cells, from which we and all animals are created, contain small internal power units called mitochondria. The processes that happen inside these power stations are of fundamental importance to the origin of life, but we will come to that in due course. Mitochondria function as chemical engines that provide energy for the cell and, by extension, the organism. In simple terms, mitochondria resemble bacteria. They are roughly the same size as bacteria and, just like bacteria, have circular strings of DNA as their own genome, which are independent of the vast majority of a cellâs genetic information, safely housed in the nucleus.
That engulfing of one life-form into the other was not a meal, but a hostile takeover. The engulfed would never be free again, but enabled previously impossible growth in its new host. It came with its own genome, with thousands of genes. Over time, most have been lost to natural selection, or migrated to the hostâs nucleus control center. But the mitochondria retains an independent set of genes to this day, almost all of which are devoted to maintaining the energy generation for cells. When this happened, charged with new energetic vigor, genomes could grow and form greater templates for evolution beyond single cells. Cells could evolve internal structures and compartments that increased specialization of cells. From there, the acquisition of coordinated communication between cells meant that an organism was not restricted to a single cell. Multicellularity followed, eventually enabling the evolution body plans for plants and animals, complex networks of cross-talking cells that interact with one another and the environment in harmony.
In backtracking through the tree of life in order to work our way back to Luca, these events provide a problem. The complication in estimating the timing and a description at the base of life comes from the fact that both bacteria and archaea do something else scientists did not expect. We pass genes down only from cell to daughter cell, from parent to child. Bacteria and archaea can swap genes, and therefore characteristics, with other individuals. Sometimes they donât even need to be of the same species to do this. This is called horizontal gene transfer (as opposed to vertical descent), and it is critical in confounding our attempts to understand the origin of life. The reason for this is because these cells donât always gain evolved functions by the typical process of descent via cell division. 12
The evolution of language is a handy metaphor here. The words
bigamy, bicycle,
and
biscuit
have a common root.
Bis
in Latin means âtwice,â so you get twice married, ride on two wheels, and eat twice-cooked tasty snacks. But there are some words or phrases that are better expressed in other languages or even absent in the recipient, and so just get pinched.
Cul-de-sac
has a slightly different and more specific meaning in English than âdead end,â so we have adopted it. The German word
Schadenfreude
has no English counterpart, but is now a splendid word in itself for ignobly enjoying your enemyâs misfortune. Yet in Swedish, the word is
skadeglädje,
derived and adapted directly from
Schadenfreude
but bypassing any common root. It has passed horizontally and subsequently evolved independently.
What this horizontal gene swapping means is that our techniques for tracking back through the
This idea was first presented by the American biologist Lynn Margulis in 1966. It caused rousing controversy and was largely rejected, and she was considered to be heretical. With time, experiments, and evidence, her views were vindicated and are now the orthodoxy. The evidence comes in a number of forms, most simply that complex cells, from which we and all animals are created, contain small internal power units called mitochondria. The processes that happen inside these power stations are of fundamental importance to the origin of life, but we will come to that in due course. Mitochondria function as chemical engines that provide energy for the cell and, by extension, the organism. In simple terms, mitochondria resemble bacteria. They are roughly the same size as bacteria and, just like bacteria, have circular strings of DNA as their own genome, which are independent of the vast majority of a cellâs genetic information, safely housed in the nucleus.
That engulfing of one life-form into the other was not a meal, but a hostile takeover. The engulfed would never be free again, but enabled previously impossible growth in its new host. It came with its own genome, with thousands of genes. Over time, most have been lost to natural selection, or migrated to the hostâs nucleus control center. But the mitochondria retains an independent set of genes to this day, almost all of which are devoted to maintaining the energy generation for cells. When this happened, charged with new energetic vigor, genomes could grow and form greater templates for evolution beyond single cells. Cells could evolve internal structures and compartments that increased specialization of cells. From there, the acquisition of coordinated communication between cells meant that an organism was not restricted to a single cell. Multicellularity followed, eventually enabling the evolution body plans for plants and animals, complex networks of cross-talking cells that interact with one another and the environment in harmony.
In backtracking through the tree of life in order to work our way back to Luca, these events provide a problem. The complication in estimating the timing and a description at the base of life comes from the fact that both bacteria and archaea do something else scientists did not expect. We pass genes down only from cell to daughter cell, from parent to child. Bacteria and archaea can swap genes, and therefore characteristics, with other individuals. Sometimes they donât even need to be of the same species to do this. This is called horizontal gene transfer (as opposed to vertical descent), and it is critical in confounding our attempts to understand the origin of life. The reason for this is because these cells donât always gain evolved functions by the typical process of descent via cell division. 12
The evolution of language is a handy metaphor here. The words
bigamy, bicycle,
and
biscuit
have a common root.
Bis
in Latin means âtwice,â so you get twice married, ride on two wheels, and eat twice-cooked tasty snacks. But there are some words or phrases that are better expressed in other languages or even absent in the recipient, and so just get pinched.
Cul-de-sac
has a slightly different and more specific meaning in English than âdead end,â so we have adopted it. The German word
Schadenfreude
has no English counterpart, but is now a splendid word in itself for ignobly enjoying your enemyâs misfortune. Yet in Swedish, the word is
skadeglädje,
derived and adapted directly from
Schadenfreude
but bypassing any common root. It has passed horizontally and subsequently evolved independently.
What this horizontal gene swapping means is that our techniques for tracking back through the
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