Are We Really 99% Chimp?

Summary

The video script explores the myth that humans share 99% of DNA with chimpanzees, highlighting the complexities of genetic comparison. It explains that while we do share a significant genetic similarity, the actual percentage is less due to large sections of DNA that are mismatched or excluded from comparison. The script also points out that DNA differences, even small ones, can lead to significant changes in traits, emphasizing that DNA comparison is more nuanced than mere percentage calculations. It concludes by stressing the value of DNA in understanding evolutionary relationships, despite the challenges.

Takeaways

• 🧬 Humans share a significant percentage of DNA with other species, such as 50% with bananas, 80% with dogs, and 99% with chimpanzees.
• 🌿 Despite the high percentage, the genetic similarities do not translate to identical DNA sequences due to mutations and natural selection over millions of years.
• 🔄 Humans and chimpanzees diverged from a common ancestor about 6 to 8 million years ago, leading to unique genetic changes in each species.
• 🧬 Humans have 23 pairs of chromosomes, while chimpanzees have 24, due to the fusion of two human chromosomes.
• 🔎 Large mutations have caused significant differences in the DNA sequences, such as duplications and deletions, complicating direct comparisons.
• 📊 Researchers compared the human and chimp genomes by excluding large mismatched sections, finding that 98.77% of the remaining DNA is identical.
• ⚠️ The 99% similarity figure is based on ignoring 18% of the chimp genome and 25% of the human genome.
• 🤔 The number of genetic changes does not directly correlate with the physical or behavioral differences between species.
• 🌳 DNA provides a record of evolutionary relationships, allowing scientists to refine the understanding of the evolutionary tree of life.
• 🙌 The script humorously concludes that while humans are not 99% chimp, they are 100% great ape and share some genetic similarity with bananas.

Q & A

What is the approximate percentage of DNA that humans share with bananas?

Humans share about 50% of their DNA with bananas.

How much DNA similarity is there between humans and dogs?

Humans share approximately 80% of their DNA with dogs.

What is the genetic similarity between humans and chimpanzees, and what does it imply?

Humans share 99% of their DNA with chimpanzees, but this figure is based on excluding large mismatched sections of the genome.

How many pairs of chromosomes do humans have compared to chimpanzees?

Humans have 23 pairs of chromosomes, while chimpanzees have 24 pairs.

What are some of the mutations that have occurred in the human and chimpanzee genomes since they diverged from a common ancestor?

Mutations include the fusion of two human scrolls, leaving 23 pairs of chromosomes, and large mutations that revised sections of DNA by duplicating or erasing chunks.

How did researchers handle the large mismatched sections of DNA when comparing human and chimpanzee genomes?

Researchers excluded the large mismatched sections, which accounted for 1.3 billion letters of DNA, and compared the remaining 2.4 billion letters on a letter-by-letter basis.

What percentage of the remaining DNA was found to be identical after excluding the large mismatched sections?

After excluding the large mismatched sections, 98.77% of the remaining DNA was found to be identical.

How does a small mutation in DNA affect the traits of an organism?

A small mutation in DNA can sometimes produce significant changes in an organism's appearance or behavior, while other times many mutations may have little effect.

What can be learned from comparing the genomes of different organisms?

Comparing genomes can reveal evolutionary relationships between organisms, even though the record is complex and requires careful analysis.

What is the significance of the evolutionary trees in understanding the relationships between species?

Evolutionary trees help refine our understanding of how species are related over time, providing a visual representation of their divergence and common ancestry.

What is the humorous claim made about humans in relation to great apes and bananas?

The script humorously claims that while humans may not be 99 percent chimpanzee, they are 100 percent great ape and at least a little bit bananas.

Outlines

00:00

🧬 Human-Chimp DNA Comparison

The paragraph discusses the common misconception that humans and chimpanzees share 99% of their DNA. It explains that while there are similarities, the genomes have diverged significantly since our last common ancestor. The human genome has 23 pairs of chromosomes compared to chimps' 24 due to a fusion event. Large mutations have altered sections of DNA, and researchers have had to grapple with how to compare duplicated or relocated genetic sequences. By excluding large mismatched sections, a 98.77% similarity was found when comparing the remaining DNA, but this approach has limitations. The paragraph also touches on the idea that DNA mutations can have varying effects on an organism's traits, and that DNA can reveal evolutionary relationships despite its complexity.

Keywords

💡DNA

DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. It is composed of a long chain of nucleotides, each containing a sugar molecule, a phosphate group, and one of four types of nitrogenous bases. In the video, DNA is central to the discussion of genetic similarities and differences between humans and other species, such as bananas, dogs, and chimpanzees. The script mentions how DNA comparisons reveal the evolutionary relationships and genetic mutations that have occurred over millions of years.

💡Chromosomes

Chromosomes are thread-like structures made of DNA and proteins, found in the nucleus of cells. They carry genetic information in the form of genes. The video script discusses how humans have 23 pairs of chromosomes, compared to chimpanzees' 24 pairs, highlighting a significant genetic difference between the two species. This difference is a result of evolutionary changes since humans and chimps diverged from a common ancestor.

💡Genomes

A genome refers to the complete set of genetic information of an organism, including all of its DNA, genes, and chromosomes. The video script uses the term 'genomes' to describe the entirety of genetic material in humans and chimpanzees. It emphasizes the complexity of comparing these genomes, given the large sections of DNA that have been duplicated, erased, or rearranged over evolutionary time.

💡Mutations

Mutations are changes in the DNA sequence that can occur naturally or can be induced by external factors. They can lead to alterations in the structure or function of genes and can be passed on to offspring. In the context of the video, mutations are discussed as the driving force behind genetic differences between species. The script explains how mutations, both large and small, have contributed to the divergence of human and chimpanzee DNA over millions of years.

💡Natural Selection

Natural selection is a key mechanism of evolution, where organisms with traits that are better suited to their environment are more likely to survive and reproduce. The video script mentions natural selection as one of the factors that have led to the genetic differences between humans and chimpanzees since their divergence from a common ancestor. It implies that certain genetic changes have been favored over time due to their advantageous effects on survival and reproduction.

💡Genetic Paragraphs

In the script, 'genetic paragraphs' is a metaphor for large sections of DNA that contain thousands of nucleotides. The video uses this term to illustrate the complexity of comparing human and chimpanzee genomes, especially when these sections appear in different numbers or orders in the two species. The concept is used to explain how genetic duplications or deletions can make direct comparisons challenging.

💡Evolutionary Relationships

Evolutionary relationships refer to the connections between different species based on their shared ancestry and the genetic changes that have occurred over time. The video script discusses how DNA comparisons can reveal these relationships, even though the record is 'garbled' due to the complexities of genetic mutations and rearrangements. The concept is central to understanding the genetic similarities and differences between humans and other primates.

💡Genetic Similarity

Genetic similarity refers to the degree of shared genetic material between organisms. The video script addresses the common misconception that humans share 99% of their DNA with chimpanzees, clarifying that this figure is derived from a comparison that excludes large sections of mismatched DNA. The concept is important for understanding the close, but not identical, genetic relationship between humans and chimpanzees.

💡Genetic Differences

Genetic differences are the variations in DNA sequences between individuals or species. The video script emphasizes that even small genetic differences can result in significant changes in an organism's appearance or behavior. It also points out that the number of genetic differences does not always correlate with the degree of similarity or difference between species, as some mutations have a more profound impact than others.

💡Evolutionary Trees

Evolutionary trees, also known as phylogenetic trees, are diagrams that illustrate the evolutionary relationships among various biological species or other entities based on their genetic similarities and differences. The video script mentions that comparing genomes has allowed scientists to refine these trees, providing a clearer picture of how different species are related to one another over evolutionary time.

💡Great Ape

Great apes are a group of primates that includes humans, chimpanzees, gorillas, orangutans, and bonobos. The term is used in the video script to emphasize the close evolutionary relationship between humans and these other primates. Despite the genetic differences highlighted in the script, humans are classified as great apes, sharing a significant portion of our genetic heritage with chimpanzees and other members of this group.

Highlights

Humans share 50% of their DNA with bananas, 80% with dogs, and 99% with chimpanzees.

The human and chimp genomes have been changed by chance, mutations, and natural selection since our last common ancestor.

Humans have 23 pairs of chromosomes compared to chimps' 24 due to the fusion of two human scrolls.

Large mutations have revised sections of DNA, duplicating and erasing chunks in both human and chimp genomes.

Tiny mutations have swapped single letters throughout the DNA of humans and chimps.

Researchers compared the chimp and human genomes by tallying single-letter differences.

Large mismatched sections of DNA were excluded from the comparison, totaling 1.3 billion letters.

After excluding mismatched sections, the remaining 2.4 billion letters of DNA were found to be 98.77% identical.

The 99% DNA similarity with chimps is based on ignoring 18% of their genome and 25% of ours.

DNA mutations can have varying impacts on an organism's appearance and behavior.

Counting genetic changes does not fully indicate the similarity or difference between two creatures.

DNA contains a record of evolutionary relationships between organisms, despite being a garbled record.

By closely reading DNA, we can refine the evolutionary trees and understand relationships between species.

We may not be 99% chimp, but we are 100% great ape and share a connection with bananas.

This episode was sponsored by Squarespace, enabling website creation without coding or web design experience.

Listeners can try Squarespace for free and get 10% off their first purchase using the promo code provided.

Transcripts

It’s often said that we humans share 50 percent of our DNA with bananas, 80 percent

with dogs, and 99 percent with chimpanzees.

Taken literally, those numbers make it sound like we could pluck one cell from a chimp

and one from a human, pull out the tangled bundles of DNA known as chromosomes, unroll

each one like a scroll, and read off two nearly identical strings of letters.

But in reality, the human and chimp scrolls don’t sync up so easily.

In the six to eight million years since we split from our last common ancestor, chance

mutations and natural selection have changed each of our genomes in radical – and unique

– ways.

Two human scrolls fused, leaving us with 23 pairs of chromosomes to chimps’ 24.

Other large mutations revised huge sections of text – duplicating a chunk of a human

DNA here, erasing a chunk of chimp DNA there – while, throughout the scrolls, tiny mutations

swapped one letter for another.

When researchers sat down to compare the chimp and human genomes, those single-letter differences

were easy to tally.

But the big mismatched sections...weren’t.

For example, if a genetic paragraph - thousands of letters long - appears twice in a human

scroll, but only once in its chimp counterpart, should the second copy count as thousands

of changes, or just one?

And what about identical paragraphs that appear in both genomes, but in different places,

or in reverse order, or broken up into pieces?

Rather than monkey around with these difficult questions, the researchers simply excluded

all the large mismatched sections – a whopping 1.3 billion letters of DNA – and performed

a letter-by-letter comparison on the remaining 2.4 billion, which turned out to be 98.77%

identical.

So, yes, we share 99% of our DNA with chimps - if we ignore 18 percent of their genome

and 25 percent of ours.

And there's another problem: just as a small tweak to a sentence can alter its meaning

entirely or not at all, a few mutations in DNA sometimes produce big changes in a creature's

looks or behavior, whereas other times lots of mutations make very little difference.

So just counting up the number of genetic changes doesn't really tell us that much about

how similar or different two creatures are.

But that doesn’t mean we can’t learn anything by comparing their genomes.

DNA contains a record of the evolutionary relationships between all organisms.

It’s a garbled record – but by reading closely, we’ve been able to glean enough

information to refine the evolutionary trees we started drawing long before genome sequencing

was around.

We may not actually be 99 percent chimp, but we are 100 percent great ape...and at least

a little bananas.

Hi, this is Emily.

This episode was brought to you in part by Squarespace, the company that will allow you,

even if you have no coding or web design experience whatsoever, to make a website in 2015 that

looks and acts like a website from 2015 – which is to say, beautiful and functional on your

smartphone and in your browser.

Go to Squarespace.com/minuteearth to try Squarespace out for free, with no credit card required,

and get 10% off your first purchase.