In my previous blog, I argued that the new BBC Evolution series lets down its audience by presenting a simple dichotomy between God and evolution. The presenter, Chris Packham, makes statements of atheistic presuppositions as if they were the findings of modern science. I argued that the series becomes incoherent as he finds himself ascribing purpose and agency to a process that he also describes as “blind”.
Now I will examine in detail the descriptions and explanations of the origin of life and LUCA (“last universal common ancestor”) in Episode 1 of the series. As introduced in my first post, I will be asking: (1) How scientifically accurate is it? and (2) How well does it fulfil the public service obligations of the BBC? This post will address the first question.
Science is a way of knowing that relies on evidence from the natural world. It formulates hypotheses about the natural world and seeks to test them against real-world evidence. If they stand up well to these tests, they become part of human knowledge. But the knowledge science gives us is always provisional and never final. It relies on an interaction of evidence, theory and presupposition – and all of these are open to revision, extension and change.
I think the BBC Evolution series tends to present science as a collection of facts that can be strung together to tell a true story. Acknowledgement of uncertainty, and accurate descriptions of the evidential support for hypotheses (and the presuppositions underlying them), are scanty throughout. The section on LUCA and the origin of life is a case in point.
Packham describes LUCA as if it was simply a fact, not a hypothesis arising from evidence. In his highly positive review of the series in the Financial Times, Prof. Adam Rutherford offers a mild corrective, calling LUCA a “hypothetical but necessarily real organism”. Although slightly oxymoronic, this statement at least expresses something about epistemology.
It is unfortunate that Packham does not use the word “hypothetical” (or a word with similar meaning), but repeatedly presents LUCA as a simple fact. This means that many viewers may end up thinking that LUCA is evidence for evolution, whereas in fact, evolution is evidence for LUCA.
Chris Packham introduces the concept of LUCA with an elephant behind him, saying:
In fact, we can trace this chain of [elephant] cells back over unimaginable periods of time through many long-lost extinct species until remarkably it converges at a single point: a single-celled organism that’s connected to every living thing, every branch on the tree of life, a common ancestor that lived billions of years ago.
When he refers to tracing back cells, I understand him to be talking about phylogenetic analysis. This is a commonly used approach in evolutionary biology that examines similarities and differences between existing life forms (especially in DNA), using them to build a tree-like structure converging in an ultimate single “trunk”.
Phylogenetic analysis assumes a tree-like structure and it assumes a single origin. The main question the method seeks to answer is “What is the ordering of the branches?”. The existence of the tree itself, and its single starting node, is not part of the question, it is a presupposition.
Packham’s description seems to reverse this. He claims that it is remarkable that the tracing back of the elephant cells “converges at a single point”.
It is not “remarkable”, it is an assumption of the methodology. There is nothing surprising about the convergence to a single point because it was the starting presupposition. Packham makes it sound as if the analysis gives us evidence for the single origin, but this is not the case. The single origin is an assumption that makes the method possible.
The single origin is an assumption that makes the method possible.
Thus, Packham presents a presupposition as if it is a conclusion from evidence. We have seen this reversal of logic before in the series (see blog post Part 2). This is confusing for the viewer, and unfortunately means we are not given a real understanding of how science works.
To be fair, some minutes later, Packham does a better job at presenting evidence for LUCA:
There are no fossils of LUCA, but because all living things have DNA and use the same genetic code, we know there must be a shared origin.
This is a better statement of evidence. The observation that all life uses the DNA molecule as hereditary material and, in addition to that (with a few notable exceptions) all life uses the same coding system to go from DNA bases to protein amino acids is indeed evidence for a single common origin of life (I will discuss this further in the next post).
Another aspect of the Episode that is confusing for the viewer is that it tends to describe LUCA as if it were the first successfully self replicating cell. Packham’s words tend to conflate LUCA and the origin of life
Packham’s words tend to conflate LUCA and the origin of life
Packham calls LUCA “The cell that started everything”. He says:
LUCA defines the point where the story of life as we know it truly began…We know that LUCA wasn’t the first cell and that it lived amongst other cells, but what made it special is that it didn’t just live; it thrived. It survived. That little bubble of chemicals formed in chaos billions of years ago. LUCA was the little cell that could. Plucky, yes. Lucky, almost certainly. But it also has life’s greatest survival trick. LUCA can copy itself well enough to keep its genetic line going…
I am not a specialist on LUCA, but I am pretty sure that Packham’s description of it as the first successfully replicating cell is out of line with what most experts think. I think it is widely believed that LUCA had progenitors, which would have been simpler. Nor is it necessary to think that LUCA had any particular advantage over other self-replicating cells around it: even if they were all the same in their abilities, over time genetic drift would mean that only one of them would be LUCA.
Perhaps Packham is just trying to do a bit too much in a few sentences – but to my mind he could have spent fewer words waxing lyrical about (what he takes to be) the implications of LUCA and more on the evidential basis for LUCA and clear explanation of theory.
More disappointing to me was that Packham hardly seems to acknowledge the big question of where LUCA came from. All he has to say about it is that LUCA was:
That little bubble of chemicals formed in chaos billions of years ago
Does he refer here to random movement of molecules, or is he referring to the primordial chaos of Greek mythology? It is not clear. “Formed in chaos” is not a compelling explanation for the origin of a complex entity.
“Formed in chaos” is not a compelling explanation for the origin of a complex entity.
The failure to address where LUCA came from is made the more surprising by Packham’s verbal description of its complexity. During his segment on LUCA, he examines some present-day microbes and says:
The cells in here are amongst the most complex things in the known universe. Each one of these cells is generating energy, distributing that energy, dealing with waste. It’s sensitive to its environment. It’s reproducing. Every one of these cells is more complex than any machine ever made by any human. Just like these cells, LUCA was complex, robust, resilient, which may have helped it cling on against the odds.
How did a cell “more complex than any machine ever made by any human” come to be “formed in chaos”. One might easily assume that it must also have been “made” by a powerful and intelligent agent. But at the start of the episode Packham told us in no uncertain terms that life has not been “made”. How then does he think life came to be?
As far as I can see, as an atheist Packham would have to hypothesise a very, very large dose of luck to explain the origin of life. How could a cell form in chaos without a huge amount of luck (if you are excluding God as a possibility)? Other atheists, like Richard Dawkins, are very candid about this, and clearly invoke huge amounts of luck to try to explain the origin of life.
Yet, surprisingly, Packham’s only reference to luck is “Plucky, yes, lucky, almost certainly.” I am not quite sure what he is referring to in that statement, but if this is about the origin of life he it would have been more appropriate for him to say “Very, very lucky, very, very definitely”. The level of luck involved would be so immense as to defy comprehension.
Ironically, if Packham had not tended to conflate LUCA with the origin of life he could have a slightly more plausible explanation of its origin. However, this would not have made a huge difference to his case, as it is hard to imagine any replicating cell that is not complex. It would need to have molecular machines within it that, at the very least, can process energy and make copies of an information-carrying molecule. The probability of these coming about by unguided processes are obviously immensely low.
On a visual note, I found it a pity that, despite Packham’s words describing the complexity of cells, the BBC animations do not attempt to convey this complexity. LUCA is depicted by CGI as a simple bag-like structure containing a few blobs.
LUCA is depicted by CGI as a simple bag-like structure containing a few blobs
A study published in Nature Ecology and Evolution in 2024 says: “Phylogenetic reconciliation suggests that LUCA had a genome…encoding around 2,600 proteins, comparable to modern prokaryotes. Our results suggest LUCA was a prokaryote-grade anaerobic acetogen that possessed an early immune system.” They say “We find strong support for the presence of ATP synthase”, which is a highly complex rotary motor.
Even though the Evolution series includes 79 minutes of photoreal CGI, imagining what 20 different extinct creatures could have looked like, no attempt was made to zoom in and illustrate what modern biology has revealed about the interior of living cells. If the viewers had for a moment seen something of the complexity of the molecular machines described in the 2024 study, it would have underlined Packham’s statements about cellular complexity and at the same time raised questions about his claim that LUCA could have been a “little bubble of chemicals formed in chaos”.
You could respond to my points here by saying “The BBC had a lot of ground to cover in a series on Evolution, so it is fair enough that they did not have a segment on the origin of life. After all, most evolutionary biologists would say that the origin of life does not fall within the category of evolution as evolution cannot start without life already being in place.” I would accept this argument if Packham had said something to this effect, and admitted that he did not know how life originated, or that all he has to go on is massive amounts of luck. But instead, to my ear at least, he makes it sound like a trivial problem, and something that can simply be taken for granted.
In conclusion, in terms of accurate depiction of science, the section on LUCA could have been done a lot better. In my view, Packham should have made it clear that LUCA is a hypothesis, not a fact. He should have described the evidence for it more clearly, in a way that distinguished between the presuppositions and the conclusions of scientific methods. He could have more clearly distinguished between LUCA and the origin of life. I also wish that the BBC animation team had attempted to depict cellular complexity, and Packham had more clearly addressed the question of the origin of life.
You might think I am being a bit picky here, but I assure you that I am being far less picky than another scientist would be if they were reviewing one of my papers. The number of people that will watch the BBC Evolution series is far larger than the number of people who will read my papers, even if they are published in Science or Nature. And what the BBC audience learns may have great influence about how they think about the big questions of life. In this context, I will give some thoughts in my next post about how the series’ treatment of LUCA fits the public service obligations of the BBC.
Featured image: Still from BBC Evolution series 2026