Tracing Back the Apple: What DNA Analysis Can Tell Us about Evolution

When thinking about ancestry, one can imagine a large apple tree. This tree has various branches, each with its own unique sets of smaller branches and red apples attached to the ends. Over time, these apples ripen and then fall. Eventually, the seeds from these apples are deposited into the soil—growing a whole new apple tree with its own unique set of branches, and shiny red apples. As you may have already guessed, the branches represent different categories: mammals, reptiles, insects—and the apples represent all living beings. Evolutionary scientists analyze these trees; investigating when certain branches came into, and others faded out of, existence. However, how are they able to trace back these ‘apples’? The answer to this is through the amazing practice of DNA analysis! 

Deoxyribonucleic acid (DNA), is a structure inside all living cells. In this structure, genetic material is stored and sorted. In biomedical settings, researchers can analyze DNA to screen for possible genetic disorders or chromosomal abnormalities. In evolutionary research, DNA analysis can be used to draw conclusions about past species, and what current species could have evolved from them. Specifically, this can be done by examining specific sequences and genes.  When two species possess the same gene for a similar function, it is thought that they are more closely related to each other. Likewise, the more different the genes, the more distantly related the species are. DNA samples in living organisms can be extracted from cells, and in fossils, they can be extracted from bone. As a hypothetical example, if a type of monkey shared a 45 percent gene similarity to an ape species, and a 78 percent gene similarity to another monkey species, it could be deduced that the two monkey species are more closely related. 

Examples of Current Research 

A research study done at Cornell University analyzed over 300 DNA samples from a multitude of sled dogs, primarily Siberian Huskies and Alaskan Malamutes. Led by Heather Huson, a previous sled dog owner herself, this study revealed that sled dogs descended from two different lineages of arctic canines, rather than one, as previously thought before. One lineage possesses the smaller frame of modern Siberian Huskies, and the other possesses the larger frame of modern Alaskan Malamutes. Huson and her team believe these analyses are crucial for understanding and protecting arctic lineages.  

In Grotte Mandrin, located in Mediterranean France, a male Neandertal skeleton was discovered and subsequently named Thorin, after a character from J.R.R Tolkein’s, The Hobbit. Led by Archaeologist Ludovic Slimac and population geneticist Martin Sikora, genetic analyses were conducted on the remains. It was found that Thorin is closely related to a lineage of Neandertals that diverged from European Neandertals around 100,000-105,000 years ago. Interestingly, this divergence coincided with an interglacial period across Eurasia, where the changing and warming environment increased warm-adapted animal populations. Through further analysis of genetic exchanges through populations, it was deduced that Thorin belonged to a largely isolated group of Neandertals that resided in Europe around 50,000 years ago. This research sheds light on Neandertal populations throughout Eurasia and contributes to the ongoing discussion of how they fell into extinction.  

Conclusion 

The tree of life is incredibly intricate and intertwined. DNA analysis can reveal a lot about what branches are related to each other, and what trees certain apples fell from. In learning about relatedness, we can uncover truths behind the origins of certain behaviors and physical features, alongside what led to certain extinctions, and how ancestral lineages can be protected.   

References  

1. MedlinePlus: What is DNA?
2. Cleveland Clinic: DNA Test – Genetic Testing
3. Anthropological Genetics: Inferring the History of Our Species Through the Analysis of DNA
4. Evidence for Evolution
5. Genomics reveal sled dogs’ Siberian lineage
6. Long genetic and social isolation in Neandertals before their extinction