Биологийн хувьсал нь зөвхөн санамсаргүй тохиолдлоор бус, харин амьд организмын удамшлын тогтвортой байдлыг хангах чиглэлд тодорхой зүй тогтлоор явагддаг болохыг судалгаагаар илрүүлжээ.
Технионы Израилийн Технологийн Институтийн судлаач Наама Бреннер тэргүүтэй багийнхан PNAS сэтгүүлд нийтлүүлсэн судалгаандаа хувьслын явцыг математик загварчлалаар судалсан байна. Биологид “дегенераци” гэж нэрлэгддэг, өөр өөр замаар ижил түвшний дасан зохицол, фитнест хүрдэг үзэгдлийг тэд шинжилжээ. Уламжлалт онолоор бол ижил түвшний фитнест хүрсэн организмууд санамсаргүй байдлаар хувьсдаг гэж үздэг байсан бол шинэ судалгаагаар үүнийг үгүйсгэв.
Судалгааны үр дүнгээс харахад организмууд хамгийн өндөр фитнест хүрснийхээ дараа мутаци болон гадны нөлөөнд хамгийн тэсвэртэй, “тэгш” бүсүүд рүү чиглэсэн хувьслыг үргэлжлүүлдэг болох нь тогтоогджээ. Энэхүү “чиглэлт шилжилт” нь тухайн популяцийн шинж чанарыг гадны сөрөг өөрчлөлтөөс хамгаалах давуу талыг бий болгодог байна.
Энэхүү нээлт нь хувьслын онолд шинэ өнцөг нээж байгаа бөгөөд амьд организмууд ямар нэгэн тусгай дарамт шахалтгүйгээр аяндаа тогтвортой, тэсвэртэй болох механизмтайг харуулж байна. Цаашид уг судалгааны аргачлалыг хиймэл оюун ухааны нейрон сүлжээний үйл ажиллагаа болон нарийн нийлмэл экосистемийн судалгаанд ашиглах боломжтой юм.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
The basics of evolution are pretty straightforward to grasp: organisms better equipped to survive and reproduce tend to have the advantage over others. These animals live on, while others don’t.
Biologists sometimes think about this as a three-dimensional fitness ‘landscape’, where the peaks are the species in the best shape. However, there are multiple routes up to the peaks of this landscape, and questions around what happens when multiple phenotypes (biological traits) are together on the same level.
Traditionally, the consensus has been that evolution proceeds randomly or neutrally at that point, but not according to a new study published in PNAS, by researchers from the Technion Israel Institute of Technology.
“Evolution is commonly described as a process of climbing fitness peaks, in which organisms become better adapted to their environment and thus improve their chances of survival,” says biologist Naama Brenner.
“However, organisms sometimes face multiple evolutionary trajectories that all yield the same level of fitness.
“This raises the question of how evolution selects among these paths of equivalent fitness.”
In biology, this arrival of multiple organisms at the same fitness peaks is called degeneracy. Biological landscapes are often highly degenerate, in that many species are roughly matched on fitness, even if they get there in different ways.
“Intuitively, one may imagine that evolution then proceeds to wander randomly among these degenerate states,” write the researchers in their published paper. “We here show that this is generally not so.”
The researchers built a simplified mathematical model to analyze how populations survive on landscapes that are flat and degenerate, factoring in the natural selection and mutation events that would happen in the real world.
Further predictions and simulations were then used to test the effects of hundreds of generations of evolution and how they might play out.
Something different to the randomness hypothesis emerged: when organisms reached the point of maximum fitness, they continued moving along it towards the flattest point, even when there was no ‘fitness advantage’.
This “directional drift” moves towards areas where a population’s particular traits are better protected against mutations and other disruptions. That’s where the survival advantage has an influence – the more forgiving parts of the map.
“On smooth manifolds of equal fitness, an implicit bias appears, directing evolving populations deterministically toward flatter regions,” write the researchers. “This bias emerges from interaction between population variability and landscape geometry.”
There are some significant implications for evolutionary theory here, the researchers point out. Evolving groups can develop robustness and resilience through this directional drift, almost as a side effect, without any specific evolutionary pressure.
The study team also argues that slight biological variations might be more important than previously thought, perhaps revealing the underlying shape of the fitness landscape and how a population has traveled along it through evolutionary history.
It’s an idea that previous studies have also looked into, while approaching it from a slightly different angle through the concept of ‘mutation-friendly neighborhoods’ – safer spaces where genetic variations come with less survival cost.
Future research could potentially link the findings to deep learning systems, where the neural networks that power AI also have a preference for flatter parts of the map.
There might also need to be a rethink around how evolutionary change is interpreted by scientists, particularly if it appears to be neutral. The next steps will be to take the relatively basic models that were used here and develop them to be used with more complex living organisms and ecosystems, as well as natural variability recorded in the wild.
Related: The ‘Shadow’ in Evolution That Explains Why Long Life Comes at a Cost
“Our results highlight a general mechanism by which degeneracy shapes long-term evolutionary outcomes, affecting our interpretation of phenotypic variability, robustness, and neutrality in high-dimensional biological systems,” write the researchers.
The research has been published in PNAS.
This article was fact-checked by Fiona MacDonald and edited by Fiona MacDonald. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.
