From the archive, originally posted by: [ spectre ]
HORIZONTAL GENE TRANSFER
Does evolution select for faster evolvers?
It’s a mystery why the speed and complexity of evolution appear to
increase with time. For example, the fossil record indicates that
single-celled life first appeared about 3.5 billion years ago, and it
then took about 2.5 billion more years for multi-cellular life to
evolve. That leaves just a billion years or so for the evolution of
the diverse menagerie of plants, mammals, insects, birds and other
species that populate the earth.
New studies by Rice University scientists suggest a possible answer;
the speed of evolution has increased over time because bacteria and
viruses constantly exchange transposable chunks of DNA between
species, thus making it possible for life forms to evolve faster than
they would if they relied only on sexual selection or random genetic
“We have developed the first exact solution of a mathematical model of
evolution that accounts for this cross-species genetic exchange,” said
Michael Deem, the John W. Cox Professor in Biochemical and Genetic
Engineering and professor of physics and astronomy.
The research appears in the Jan. 29 issue of Physical Review Letters.
Past mathematical models of evolution have focused largely on how
populations respond to point mutations – random changes in single
nucleotides on the DNA chain, or genome. A few theories have focused
on recombination – the process that occurs in sexual selection when
the genetic sequences of parents are recombined.
Horizontal gene transfer (HGT) is a cross-species form of genetic
transfer. It occurs when the DNA from one species is introduced into
another. The idea was ridiculed when first proposed more than 50 years
ago, but the advent of drug-resistant bacteria and subsequent
discoveries, including the identification of a specialized protein
that bacteria use to swap genes, has led to wide acceptance in recent
“We know that the majority of the DNA in the genomes of some animal
and plant species – including humans, mice, wheat and corn – came from
HGT insertions,” Deem said. “For example, we can trace the development
of the adaptive immune system in humans and other jointed vertebrates
to an HGT insertion about 400 million years ago.”
The new mathematical model developed by Deem and visiting professor
Jeong-Man Park attempts to find out how HGT changes the overall
dynamics of evolution. In comparison to existing models that account
for only point mutations or sexual recombination, Deem and Park’s
model shows how HGT increases the rate of evolution by propagating
favorable mutations across populations.
Deem described the importance of horizontal gene transfer in the work
in a January 2007 cover story in the Physics Today, showing how HGT
compliments the modular nature of genetic information, making it
feasible to swap whole sets of genetic code – like the genes that
allow bacteria to defeat antibiotics.
“Life clearly evolved to store genetic information in a modular form,
and to accept useful modules of genetic information from other
species,” Deem said.
Source: Rice University
mwdeem [at] rice [dot] edu
Phase Diagrams of Quasispecies Theory with Recombination and
Horizontal Gene Transfer
Authors: Jeong-Man Park, Michael W. Deem
We consider how transfer of genetic information between
individuals influences the phase diagram and mean fitness of both the
Eigen and the parallel, or Crow-Kimura, models of evolution. In the
absence of genetic transfer, these physical models of evolution
consider the replication and point mutation of the genomes of
independent individuals in a large population. A phase transition
occurs, such that below a critical mutation rate an identifiable
quasispecies forms. We generalize these models of quasispecies
evolution to include horizontal gene transfer. We show how transfer of
genetic information changes the phase diagram and mean fitness and
introduces metastability in quasispecies theory, via an analytic field
Nobel Prize genius Crick was high on LSD
when he discovered the secret of life
August 8, 2004
BY ALUN REES
FRANCIS CRICK, the Nobel Prize-winning father of modern genetics, was
under the influence of LSD when he first deduced thedouble-helix
structure of DNA nearly 50 years ago.
The abrasive and unorthodox Crick and his brilliant American co-
researcher James Watson famously celebrated their eureka moment in
March 1953 by running from the now legendary Cavendish Laboratory in
Cambridge to the nearby Eagle pub, where they announced over pints of
bitter that they had discovered the secret of life.
Crick, who died ten days ago, aged 88, later told a fellow scientist
that he often used small doses of LSD then an experimental drug used
in psychotherapy to boost his powers of thought. He said it was LSD,
not the Eagle’s warm beer, that helped him to unravel the structure of
DNA, the discovery that won him the Nobel Prize.
Despite his Establishment image, Crick was a devotee of novelist
Aldous Huxley, whose accounts of his experiments with LSD and another
hallucinogen, mescaline, in the short stories The Doors Of Perception
and Heaven And Hell became cult texts for the hippies of the Sixties
and Seventies. In the late Sixties, Crick was a founder member of
Soma, a legalise-cannabis group named after the drug in Huxley’s novel
Brave New World. He even put his name to a famous letter to The Times
in 1967 calling for a reform in the drugs laws.
It was through his membership of Soma that Crick inadvertently became
the inspiration for the biggest LSD manufacturing conspiracy-the world
has ever seen the multimillion-pound drug factory in a remote
farmhouse in Wales that was smashed by the Operation Julie raids of
the late Seventies.
Crick’s involvement with the gang was fleeting but crucial. The
revered scientist had been invited to the Cambridge home of
freewheeling American writer David Solomon a friend of hippie LSD guru
Timothy Leary who had come to Britain in 1967 on a quest to discover a
method for manufacturing pure THC, the active ingredient of cannabis.
It was Crick’s presence in Solomon’s social circle that attracted a
brilliant young biochemist, Richard Kemp, who soon became a convert to
the attractions of both cannabis and LSD. Kemp was recruited to the
THC project in 1968, but soon afterwards devised the world’s first
foolproof method of producing cheap, pure LSD. Solomon and Kemp went
into business, manufacturing acid in a succession of rented houses
before setting up their laboratory in a cottage on a hillside near
Tregaron, Carmarthenshire, in 1973. It is estimated that Kemp
manufactured drugs worth Pounds 2.5 million an astonishing amount in
the Seventies before police stormed the building in 1977 and seized
enough pure LSD and its constituent chemicals to make two million LSD
The arrest and conviction of Solomon, Kemp and a string of co-
conspirators dominated the headlines for months. I was covering the
case as a reporter at the time and it was then that I met Kemp’s close
friend, Garrod Harker, whose home had been raided by police but who
had not been arrest ed. Harker told me that Kemp and his girlfriend
Christine Bott by then in jail were hippie idealists who were
completely uninterested in the money they were making.
They gave away thousands to pet causes such as the Glastonbury pop
festival and the drugs charity Release.
‘They have a philosophy,’ Harker told me at the time. ‘They believe
industrial society will collapse when the oil runs out and that the
answer is to change people’s mindsets using acid. They believe LSD can
help people to see that a return to a natural society based on self-
sufficiency is the only way to save themselves.
‘Dick Kemp told me he met Francis Crick at Cambridge. Crick had told
him that some Cambridge academics used LSD in tiny amounts as a
thinking tool, to liberate them from preconceptions and let their
genius wander freely to new ideas. Crick told him he had perceived the
double-helix shape while on LSD.
‘It was clear that Dick Kemp was highly impressed and probably bowled
over by what Crick had told him. He told me that if a man like Crick,
who had gone to the heart of human existence, had used LSD, then it
was worth using. Crick was certainly Dick Kemp’s inspiration.’ Shortly
afterwards I visited Crick at his home, Golden Helix, in Cambridge.
He listened with rapt, amused attention to what I told him about the
role of LSD in his Nobel Prize-winning discovery. He gave no
intimation of surprise. When I had finished, he said: ‘Print a word of
it and I’ll sue.’