‘LUCA’ – Last Universal Common Ancestor

‘Curiously, although his theory emphasized male-female distinctions, his description in the Origin always placed the primordial ancestor, or ‘the ancient progenitor’ outside, or previous to, gender or sexed system; an ‘it’, never a ‘he’ or ‘she’. Gillian Beer, Introduction to the Origin of Species 1859, Oxford University Press, 1988

‘Back before the dinosaurs, before the first fishes, before the first worms, before the first plants, before the first fungi, before the first bacteria, there was an RNA world - probably somewhere around four billion years ago, soon after the beginning of planet earth’s very existence and when the universe itsef was only 10 billion years old. We do not know what these ribo-organisms looked like. We can only guess at what they did for a living, chemically speaking. We do not what came before them. We can be pretty sure they once existed because of clues to RNA’s role that survive in living organisms today. These ribo-organisms had a big problem. RNA is an unstable susbstance which falls apart within hours. Had these organisms ventured anywhere hot or tried to grow too large they would have faced what geneticists call an error catastrophe – a rapid decay of the message in their genes. One of them invented by trial and error a new and tougher version of RNA called DNA and a system for making RNA copies from it, including a machine we’ll call the proto-ribosome. It had to work fast and it had to be accurate. So it stiched together genetic copies three letters at a time, the better to be fast and accurate. Each threesome came flagged with a tag to make it easier for the proto-ribosome to find, a tag made of amino acid. Much later, those tags themselves became joined togther to make proteins and the three letter word became a form of code for the proteins – the genetic code itself. (Hence, to this day the code consists of three letter words each spelling out a particular one of twenty amino acids as part of a recipe for a protein.) And so was born a more sophisticated creature that stores its genetic recipe in its DNA, made its working machines of protein and used RNA to bridge the gap between them. Her name was LUCA – the Last Universal Common Ancestor.’ Matt Ridley, Genome: The Autobiography of a Species in 23 Chapters, Fourth Estate, 2000

‘Last year has also witnessed the unveiling of the first molecular map of the ribosome, the cell's protein factory. This has given us startling new details about its structure and may boost support for RNA (ribonucleic acid) being the first "living" molecule on Earth.’ BBC Online


‘LUCA’ – Last Universal Common Ancestor

Even before DNA - RNA -
unstable, sucking more life

from the inchoate chemical world -
defining in the blurred creative soup

of transient genes, urging
to be, replicate - just stay.

Becoming ‘organic copier’;
stitcher, cutter and paster -

translator, builder, joiner,
fixer, connector - bridge.

Keeping itself patterned in DNA,
drawing order into possible life -

hearing the Word four billion years ago
in swimming silence, dim interpretation

of the frustrating invisibility of God -
call for creativity as a first principle;

making its own skeleton for us all,
boneless - yet imagined or dreamt.


Ur-gene, first gene; prettily named LUCA,
the ‘Last Universal Common Ancestor’ -

author of the code, writer of the three letter
words holding us in existence; maintaining

our fleshy shell, transforming wet molecules
to scaffold bone; metamorphosing chemistry

that wrote gold barley’s whiskered ear -
heaven-colour of blurred hummingbird,

shining armour of the patent beetle –
owl eye, eagle wing; old melancholy

hunchback sunflower studying earth.
The bridge translating coded stores -

DNA copied into RNA; reading the words,
translating into protein - building limb, fin,

finger, leaf; still reading ourselves,
making ourselves from glued code -

billion upon billion years rehearsing,
but never tiring, becoming dispirited;

like LUCA herself,
who wanted to be -

as earless leaves cramped
unborn within the branch

hear spring and sun.
As space and stars,

heard the Word,
dreamt of Earth.

LUCA not one, but many;
fountain of species, flood,

still printed in our word
with the worm and fish -

tree, bird -
water, star.