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[00:00.66] Scientists have wondered long on the mystery of how whales got so big.

[00:09.69] A new study suggests some answers.

[00:14.74] Whales are ocean animals. The fin, bowhead, gray, humpback and sperm whales are the largest animals living today.

[00:29.88] In fact, the blue whale is the largest animal known to have ever existed, bigger than any dinosaur.

[00:41.04] The recent study by researchers in Brazil found that four genes appear to play a big part in whales’ huge size, a condition known as gigantism.

[00:58.57] The researchers said the four genes appear to have produced great size while easing the problems linked with it, such as cancer risk and lower reproductive ability.

[01:16.37] Whales are part of the ocean animal family called Cetaceans, which includes dolphins and porpoises.

[01:26.73] Scientists think the family developed 50 million years ago from animals like wolves, but is also related to today’s cows, pigs, sheep and similar animals.

[01:45.85] Mariana Nery, a genetics expert with the University of Campinas (UNICAMP) in Brazil, was a lead writer of the report.

[01:58.07] It appeared in the publication Scientific Reports. Nery said her team has done the first study of gigantism in whales at the molecular level.

[02:12.95] She said, “Body size is a complex result of many genes, pathways, and physical and ecological processes.”

[02:24.90] The study examined seven kinds of whales that grow longer than 10 meters. Six of them are toothless animals.

[02:35.52] Instead, they have structures called baleen in their mouths that catch very small animals.

[02:45.09] The seventh species studied was the sperm whale, which has large teeth to feed on giant squid and ocean animals.

[02:56.24] The whales can reach huge sizes. Humpback and right whales can reach 15 meters in length; the sperm and bowhead whales, 18 meters; the fin whale can reach 24 meters, and the biggest, the blue whale, has been measured at 30 meters.

[03:20.42] The researchers studied several genes linked to increased body size in other animals.

[03:28.91] They found four genes that appeared to be important in the development of whales.

[03:37.15] One of the genes is GHSR.

[03:41.40] It is involved in releasing growth hormone from the pituitary gland, a part of the body that releases important chemicals.

[03:53.62] Growth hormone can cause hunger and it can control metabolism and the growth of fat. The gene also controls cell division.

[04:06.90] A second gene is called IGFBP7. This gene is involved in cell growth and division.

[04:18.59] There is evidence that this gene acts to suppress cancer in many parts of the body including the prostate, breasts, lungs, colon and rectum.

[04:34.26] NCAPG is a gene associated with growth in humans, horses, cattle, pigs and chickens.

[04:46.74] It can cause size and weight gain and affects the lives of cells.

[04:53.65] The gene PLAG1 is associated with body growth in cows, pigs and sheep.

[05:03.21] It is involved in the growth of embryos and cell survival.

[05:09.59] The study also suggests that the genes such as GHSR and IGFBP7, which are linked to huge size, might also control cell development and suppress cancer.

[05:28.18] Huge size in nature is tied to shorter lifespans. But huge whales live long lives.

[05:38.81] The humpback whale can reach 50 years of age. The blue whale can reach 90 and, the study noted, the bowhead whale is the longest-lived mammal known, reaching 200 years of age.

[06:00.06] Felipe Andre Silva was lead writer of the study.

[06:05.90] He worked on the research while earning his master’s degree in genetics and molecular biology.

[06:14.40] He said gigantism in whales appeared relatively recently, around 5 million years ago.

[06:24.49] “Before that there were animals with large sizes…but these were exceptions, and most cetaceans did not exceed 10 meters in length,” he said.

[06:39.63] Silva told Reuters news agency: “Gigantism may bring some advantages such as a lower chance of being preyed upon and a greater change of obtaining food.”

[06:56.10] Nery said a lot can be learned about the development, or evolution, of whales over long periods of time.

[07:06.99] She said, “These animals can teach us a lot about the evolutionary process itself.”

[07:15.49] And whales remain popular and interesting to many people and gain a lot of attention.

[07:23.73] Nery added, “The evolution of cetaceans is a fantastic story…”